Are the bacteria doing the same photosynthesis as plants do?

Are the bacteria doing the same photosynthesis as plants do?

We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

I mean Plants during photosynthesis produce oxygen but Do bacteria also produce oxygen during photosynthesis or produce other gases?

If yes , how do these bacteria process photosynthesis by producing other gases?

Photosynthesis is always about using solar energy to oxidize a mineral molecule and reduce an organic molecule, which becomes an energy source for the photosynthetic cell.

Bacteria and plants have different types of photoreceptors. It is not always the same chlorophyll, maybe even no chlorophyll at all ! The different colours in algae come from the different pigments they are using to do photosynthesis.

Plant cells carry out photosynthesis in chloroplasts, which are organites, whereas bacteria carry it out in their plasmic membranes.

Plants do aerobic photosynthesis, which means they reduce dioxygen into water. Some bacteria do anoxic photosynthesis, which means they can reduce hydrogen sulfide into sulfur.

Argonne and Washington University scientists unravel mystery of photosynthesis

Plants have been harnessing the sun’s energy for hundreds of millions of years.

Algae and photosynthetic bacteria have been doing the same for even longer, all with remarkable efficiency and resiliency.

It’s no wonder, then, that scientists have long sought to understand exactly how they do this, hoping to use this knowledge to improve human-made devices such as solar panels and sensors.

“ We have a tremendous opportunity here to open up completely new disciplines of light-driven biochemical reactions, ones that haven’t been envisioned by nature. If we can do that, that’s huge.” — Argonne biophysicist Philip Laible

Scientists from the U.S. Department of Energy’s ( DOE ) Argonne National Laboratory, working closely with collaborators at Washington University in St. Louis, recently solved a critical part of this age-old mystery, homing in on the initial, ultrafast events through which photosynthetic proteins capture light and use it to initiate a series of electron transfer reactions.

“ In order to understand how biology fuels all of its engrained activities, you must understand electron transfer,” said Argonne biophysicist Philip Laible. ​ “ The movement of electrons is crucial: it’s how work is accomplished inside a cell.”

In photosynthetic organisms, these processes begin with the absorption of a photon of light by pigments localized in proteins.

Each photon propels an electron across a membrane located inside specialized compartments within the cell.

“ The separation of charge across a membrane — and stabilization of it — is critical as it generates energy that fuels cell growth,” said Argonne biochemist Deborah Hanson.

The Argonne and Washington University research team has gained valuable insight on the initial steps in this process: the electron’s journey.

Nearly 35 years ago, when the first structure of these types of complexes was unveiled, scientists were surprised to discover that after the absorption of light, the electron transfer processes faced a dilemma: there are two possible pathways for the electron to travel.

In nature, plants, algae and photosynthetic bacteria use just one of them — and scientists had no idea why.

What they did know was that the propulsion of the electron across the membrane — effectively harvesting the energy of the photon — required multiple steps.

Argonne and Washington University scientists have managed to interfere with each one of them to change the electron’s trajectory.

“ We’ve been on this trail for more than three decades, and it is a great accomplishment that opens up many opportunities,” said Dewey Holten, a chemist at Washington University.

The scientists’ recent article, ​ “ Switching sides—Reengineered primary charge separation in the bacterial photosynthetic reaction center,” published in the Proceedings of the National Academy of Sciences, shows how they discovered an engineered version of this protein complex that switched the utilization of the pathways, enabling the one that was inactive while disabling the other.

“ It is remarkable that we have managed to switch the direction of initial electron transfer,” said Christine Kirmaier, Washington University chemist and project leader. ​ “ In nature, the electron chose one path 100 percent of the time. But through our efforts, we have been able to make the electron switch to an alternate path 90 percent of the time. These discoveries pose exciting questions for future research.”

As a result of their efforts, the scientists are now closer than ever to being able to design electron transfer systems in which they can send an electron down a pathway of their choosing.

“ This is important because we are gaining the ability to harness the flow of energy to understand design principles that will lead to new applications of abiotic systems,” Laible said. ​ “ This would allow us to greatly improve the efficiency of many solar-powered devices, potentially making them far smaller. We have a tremendous opportunity here to open up completely new disciplines of light-driven biochemical reactions, ones that haven’t been envisioned by nature. If we can do that, that’s huge.”

What Are Some Examples of Photosynthetic Bacteria?

Purple and green bacteria and cyanobacteria are photosynthetic. Photosynthetic bacteria are able to produce energy from the sun's rays in a process similar to that used by plants. Instead of using chlorophyll to capture the sun's light, these bacteria use a compound called bacteriochlorophyll.

Cyanobacteria are unicellular organisms that live in water. Fossilized cyanobacteria have been on Earth a long time and play an important role in the food chain. They likely generated much of the oxygen in the atmosphere and are the precursors to chloroplasts, which allow plants to make their own food. They convert nitrogen in the soil into a form that can be used by some plants.

There are two varieties of purple bacteria. One variety uses sulfur instead of oxygen to carry out the process of photosynthesis, and oxygen can actually inhibit their growth. These bacteria live in aquatic environments with oxygen deficiencies. The other variety of purple bacteria resides in oxygenated environments and requires oxygen for photosynthesis.

Like purple bacteria, some green bacteria conduct photosynthesis by using sulfur. Though often located in estuaries, green bacteria have also been discovered in the deep ocean near hydrothermal vents. Though very little light penetrates to these depths, the tiny amount of light that does is used by the green bacteria to create energy.

Cyborgs evolve

Purifying the nitrogenase enzyme from bacteria isn’t likely to scale up because it’s so time consuming. Instead Kings is hoping to show how nitrogenase works and so help synthetic chemists mimic it with easy to handle artificial analogues.

Yang sees a different way forward not deconstructing cells, but making them more elaborate. At the moment his “leaves” are simple cells, a package of enzymes and biological machinery encapsulated in a membrane. But “evolve” them into more complex cells, with internal units each equipped to do specialised chemical transformations, and you could end up with cells that work as processing lines for complex and interesting chemicals.

“We can start thinking about this as a general renewable chemical synthesis platform,” says Nocera. Because the bacteria can be genetically manipulated, it is possible to have them make plastics, pharmaceutical drugs or compounds whose synthesis would otherwise require a lot of fuel. It’s this sort of application that Nocera thinks will be the first to be economically viable. “As these processes become cheaper, the next important step would be fuel production.”

A neat stamp of approval for such ideas recently came from NASA. Yang has received a funding package from the agency’s new Center for the Utilization of Biological Engineering in Space. This outfit plans to use living organisms to produce some essentials for astronauts, including food, fuel and oxygen.

The plan will be to get Yang’s bionic leaves to pull off King’s trick of taking nitrogen and carbon dioxide and producing ammonia as fertiliser for food crops in space and oxygen to breathe. “On Earth, fuel is it and oxygen is of no value,” says Reisner. In space, of course, oxygen is crucial.

Yang is even imagining building a system that combines different types of bionic cells with various functions. These might work more like an organism, with sensing cells checking when oxygen supplies get low, for example, and getting the leaf cells to dial up their photosynthesis.

We have certainly come a long way since Yang first tried connecting his bacteria to electricity. “It’s getting closer to the movie The Martian,” says Nocera. Perhaps one day bionic leaves will eat their electrons on another planet.

This article appeared in print under the headline “Make like a leaf”

Why are plants green?

When sunlight shining on a leaf changes rapidly, plants must protect themselves from the ensuing sudden surges of solar energy. To cope with these changes, photosynthetic organisms — from plants to bacteria — have developed numerous tactics. Scientists have been unable, however, to identify the underlying design principle.

An international team of scientists, led by physicist Nathaniel M. Gabor at the University of California, Riverside, has now constructed a model that reproduces a general feature of photosynthetic light harvesting, observed across many photosynthetic organisms.

Light harvesting is the collection of solar energy by protein-bound chlorophyll molecules. In photosynthesis — the process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water — light energy harvesting begins with sunlight absorption.

The researchers’ model borrows ideas from the science of complex networks, a field of study that explores efficient operation in cellphone networks, brains, and the power grid. The model describes a simple network that is able to input light of two different colors, yet output a steady rate of solar power. This unusual choice of only two inputs has remarkable consequences.

“Our model shows that by absorbing only very specific colors of light, photosynthetic organisms may automatically protect themselves against sudden changes — or ‘noise’ — in solar energy, resulting in remarkably efficient power conversion,” said Gabor, an associate professor of physics and astronomy, who led the study appearing today in the journal Science. “Green plants appear green and purple bacteria appear purple because only specific regions of the spectrum from which they absorb are suited for protection against rapidly changing solar energy.”

Gabor first began thinking about photosynthesis research more than a decade ago, when he was a doctoral student at Cornell University. He wondered why plants rejected green light, the most intense solar light. Over the years, he worked with physicists and biologists worldwide to learn more about statistical methods and the quantum biology of photosynthesis.

Richard Cogdell, a renowned botanist at the University of Glasgow in the United Kingdom and a coauthor on the research paper, encouraged Gabor to extend the model to include a wider range of photosynthetic organisms that grow in environments where the incident solar spectrum is very different.

“Excitingly, we were then able to show that the model worked in other photosynthetic organisms besides green plants, and that the model identified a general and fundamental property of photosynthetic light harvesting,” he said. “Our study shows how, by choosing where you absorb solar energy in relation to the incident solar spectrum, you can minimize the noise on the output — information that can be used to enhance the performance of solar cells.”

Coauthor Rienk van Grondelle, an influential experimental physicist at Vrije Universiteit Amsterdam in the Netherlands who works on the primary physical processes of photosynthesis, said the team found the absorption spectra of certain photosynthetic systems select certain spectral excitation regions that cancel the noise and maximize the energy stored.

“This very simple design principle could also be applied in the design of human-made solar cells,” said van Grondelle, who has vast experience with photosynthetic light harvesting.

Gabor explained that plants and other photosynthetic organisms have a wide variety of tactics to prevent damage due to overexposure to the sun, ranging from molecular mechanisms of energy release to physical movement of the leaf to track the sun. Plants have even developed effective protection against UV light, just as in sunscreen.

“In the complex process of photosynthesis, it is clear that protecting the organism from overexposure is the driving factor in successful energy production, and this is the inspiration we used to develop our model,” he said. “Our model incorporates relatively simple physics, yet it is consistent with a vast set of observations in biology. This is remarkably rare. If our model holds up to continued experiments, we may find even more agreement between theory and observations, giving rich insight into the inner workings of nature.”

To construct the model, Gabor and his colleagues applied straightforward physics of networks to the complex details of biology, and were able to make clear, quantitative, and generic statements about highly diverse photosynthetic organisms.

“Our model is the first hypothesis-driven explanation for why plants are green, and we give a roadmap to test the model through more detailed experiments,” Gabor said.

Photosynthesis may be thought of as a kitchen sink, Gabor added, where a faucet flows water in and a drain allows the water to flow out. If the flow into the sink is much bigger than the outward flow, the sink overflows and the water spills all over the floor.

“In photosynthesis, if the flow of solar power into the light harvesting network is significantly larger than the flow out, the photosynthetic network must adapt to reduce the sudden over-flow of energy,” he said. “When the network fails to manage these fluctuations, the organism attempts to expel the extra energy. In doing so, the organism undergoes oxidative stress, which damages cells.”

The researchers were surprised by how general and simple their model is.

“Nature will always surprise you,” Gabor said. “Something that seems so complicated and complex might operate based on a few basic rules. We applied the model to organisms in different photosynthetic niches and continue to reproduce accurate absorption spectra. In biology, there are exceptions to every rule, so much so that finding a rule is usually very difficult. Surprisingly, we seem to have found one of the rules of photosynthetic life.”

Gabor noted that over the last several decades, photosynthesis research has focused mainly on the structure and function of the microscopic components of the photosynthetic process.

“Biologists know well that biological systems are not generally finely tuned given the fact that organisms have little control over their external conditions,” he said. “This contradiction has so far been unaddressed because no model exists that connects microscopic processes with macroscopic properties. Our work represents the first quantitative physical model that tackles this contradiction.”

Next, supported by several recent grants, the researchers will design a novel microscopy technique to test their ideas and advance the technology of photo-biology experiments using quantum optics tools.

“There’s a lot out there to understand about nature, and it only looks more beautiful as we unravel its mysteries,” Gabor said.

Gabor, Cogdell, and van Grondelle were joined in the research by Trevor B. Arp, Jed Kistner-Morris, and Vivek Aji at UCR.

The research was supported by the Air Force Office of Scientific Research Young Investigator Program, the National Science Foundation, and through a U.S. Department of the Navy's Historically Black Colleges and Universities/Minority Institutions award. Gabor was also supported through a Cottrell Scholar Award and a Canadian Institute for Advanced Research Azrieli Global Scholar Award. Other sources of funding were the NASA MUREP Institutional Research Opportunity program, the U.S. Department of Energy, the Biotechnological and Biological Sciences Research Council, the Royal Netherlands Academy of Arts and Sciences, and the Canadian Institute for Advanced Research.

The research paper is titled, “Quieting a noisy antenna reproduces photosynthetic light harvesting spectra.”

How do Parasitic Plants Survive Without Photosynthesis?

Some engulf their host plants, sucking their energy like a vampire sucks blood. Others tap into the forest’s underground network of fungi to feed indirectly.

These relationships are called obligate parasitism, meaning finding a host plant is essential for the parasite to live . This contrasts with other plant parasites, such as mistletoe, that can photosynthesize as well as steal nutrients.

What all achlorophyllous plants have in common is their otherworldly appearance – this is a weird bunch. Their bizarre looks have earned them names such as “ghost plant” and “wizard’s net.”

Many grow in ghostly shades of white and orange with microscopic leaves and unusual flowers. If you’re looking for more strange and magical plants check out our guide to real-world magical plants .

Since parasitic flowering plants don’t have any need for sunlight, many only appear above ground as a flower. They often lack the stems, leaves and branches that we would expect from a plant. These parasites look more like alien invaders or strange mushrooms than native plants!

Let’s take a look at a few these peculiar species of parasitic plants.


IIB Bacterial Reaction Centers

Higher plants are not the only organisms that perform photosynthesis. Algae also do, as do many bacteria. In all of them, the energy of light is converted to chemical energy in photosynthetic reaction centers. These are membrane-bound oligomeric protein complexes which contain a chlorophyll or bacteriochlorophyll dimer known as a special pair. The special pair donates an electron to an acceptor molecule following absorption of a photon. The reaction centers of plants, algae and photosynthetic bacteria resemble each other surprisingly closely. It has been suggested that they have evolved from a common ancestor. We will begin by describing bacterial reaction centers. Photosynthetic bacteria are described in more detail by Jones (2009) and Hunter et al. (2008) and reaction centers are discussed by Yocum (2008a) .

It has been possible to isolate many of the oligomeric protein complexes involved in photosynthesis by dissolving the membranes in detergent and purifying the complexes through chromatography and other techniques. The reaction centers of purple photosynthetic bacteria are embedded in the cell membrane or in the membranes of intracytoplasmic vesicles which are often called chromatophores. Hartmut Michel, Johann Deisenhofer and Robert Huber isolated reaction centers from the green-colored (!) purple bacterium Blastochloris viridis (formerly Rhodopseudomonas viridis), devised a way to crystallize them and determined their structure by x-ray diffraction ( Diesenhofer and Michel, 1989 ). This was the first crystallization of a membrane protein and paved the way for determination of the structures of many prokaryotic and eukaryotic membrane proteins. In addition, the reaction center structure provided important insights into the general properties to be expected of integral membrane proteins. The Blc. viridis reaction center consists of four subunits. Subunits L and M have similar but not identical amino acid sequences. Each comprises five α-helices that cross the membrane. The co-factors that participate in electron transport are bound to the L and M subunits. Their arrangement is sketched in Fig. 51.2 . The primary electron donor (known as P985 because a loss of optical density at 985 nm accompanies its photo-oxidation) is indeed a dimer, in this case of bacteriochlorophyll b. The reaction center also includes two additional molecules of bacteriochlorophyll b, two of bacteriopheophytin b, one molecule each of menaquinone, ubiquinone and carotenoid, and a non-heme ferrous iron ion. Bacteriopheophytin is similar to bacteriochlorophyll, but the Mg 2+ is replaced by two protons. Surprisingly, the reaction center has approximate twofold symmetry. The electrons leaving P985 move down only the L side of the reaction center. The first electron transfer, to the accessory bacteriochlorophyll b, occurs within a few picoseconds (10 −12 s). The electrons move to the bacteriopheophytin b associated with subunit L, to QA (menaquinone) and, finally, to QB (ubiquinone). Upon receiving two electrons (after two photoacts), the ubiquinone binds two protons from the periplasm as it is reduced to ubihydroquinone. The ubihydroquinone dissociates into the membrane and diffuses to a cytochrome bc1 complex, where it is re-oxidized. The reaction center also includes a cytochrome subunit containing four hemes, which is located on the periplasmic surface (facing the outside of the cell) of the membrane. The hemes donate electrons to oxidized P985. There is also an H subunit, which forms a sort of cap on the cytoplasmic side of the L and M subunits and is anchored to the membrane by a single membrane-spanning helix. Its function is not known. Purple bacterial reaction centers are embedded in the cytoplasmic membrane or in the membranes of intracellular vesicles which are often termed chromatophores.

FIGURE 51.2 . The arrangement of the co-factors in the Blastochloris viridis reaction center. The reaction center has approximate twofold (C2) symmetry, but electrons move only along the path indicated. After QB accepts two electrons, two protons from the cytoplasmic side of the membrane are bound. P985, the photochemically active bacteriochlorophyll b dimer Bchl, bacteriochlorophyll b BPheo, bacteriopheophytin b QA, menaquinone QB, ubiquinone Fe, ferrous iron.

Photosynthetic electron transport systems are capable of transporting electrons much more rapidly than photons of sunlight arrive at the special pairs. Therefore, reaction centers are accompanied by arrays of light-harvesting antenna pigments whose purpose is to capture photons and transfer the excitation energy to the special pairs. Purple bacterial reaction centers are surrounded by a “picket fence” of transmembrane dimers to which are bound bacteriochlorophyll and carotenoid molecules. The monomers, designated α and β, comprise the LH1 (light-harvesting 1) complex ( Fig. 51.3 ). The carotenoids absorb photons in the middle of the visible spectrum and quickly pass the excitation to the bacteriochlorophyll. The bacteriochlorophyll absorbs photons in the blue, red and near-infrared regions of the spectrum. The excitations become delocalized within the circle of bacteriochlorophylls within femtoseconds (10 −15 s) and are transferred to the special air in tens of picoseconds, faster than many can be lost as heat or fluorescence. Details of these processes are discussed by Blankenship (2002) .

FIGURE 51.3 . Light absorption and the transfer and capture of excitation energy. Protein dimers to which BChl and carotenoid molecules are bound form a ring around the reaction center. (Higher plant light harvesting pigments have a quite different structure.) Light is absorbed by any bacteriochlorophyll molecule (dark rectangles). The excitation energy is then delocalized among the bacteriochlorophyll molecules and finally captured by a special bacteriochlorophyll pair in the reaction center (RC). The figure is based on the structure of the bacterial light-harvesting complex reported by Cogdell et al. (1999) .

Other purple bacterial reaction centers have the same basic structure, but with variations. Most have bacteriochlorophyll α, bacteriopheophytin α and only ubiquinone. Many lack a bound cytochrome subunit. Observation of their topography by atomic force microscopy has revealed a variety of arrangements of LH1, including reaction centers multimers surrounded by continuous LH1 complexes ( Sturgis and Niederman, 2008 ). Many have peripheral light-harvesting complexes, designated LH2, LH3, etc. Like LH1, they are composed of α and β subunits arranged in cylinders. They transfer absorbed excitations to LH1.

Difference Between Photosynthesis and Chemosynthesis

Photosynthesis uses solar energy to produce glucose while chemosynthesis does not require solar energy to produce glucose.

Comparison Chart

Occurs inGreen plantsBacteria
DiscovererJan IngenhouszS.N Vinogradskii (1887)
FuelsWater, carbon dioxide and solar energyInorganic compounds
End productsGlucose and oxygenGlucose and oxygen
UsesAs fuel for lifeAs fuel for life

What is Photosynthesis?

Ecosystem depends upon the ability of organisms to convert inorganic compounds into food that other organisms use as fuel for their lives. Photosynthesis is a primary food production which is powered by solar energy. Plants and microbes cannot eat food, so they have to make food for themselves. Photosynthesis takes place in plants and some bacteria, where there is sufficient sunlight. This occurs on land, shallow water and sometimes below ice where sunlight can reach. Photosynthetic organisms species and plants convert carbon dioxide and water into sugar and oxygen by using sun light. Following formula is a description of this reaction: CO2 + 6H2O -> C6H12O6 + 6O2 Plants draw water from the soil up through roots. The water is then transferred to the leaves by particular cells of plants called xylem. Plants consume some water when other natural processes occur, and some water is used during the photosynthesis process. Plants have special cells called stomata which open and close on stimulus. Plants take carbon dioxide through the stomata and release oxygen formed during the chemical reaction of photosynthesis. Plants also lose some water during this gas exchange. Chlorophyll is a complex molecule which is present in green plants and absorb light. Any substance which absorbs light is called pigment. Pigments absorb light of a specific wavelength and reflect the rest back. Chlorophyll absorbs all wavelength of light except for green. Because of this reason, grass and leaves of trees look green. When a plant absorbs light energy or carbon dioxide, chlorophyll causes the chemical reaction which turns the light into two different substances ATP and NADPH. ATP stands for adenosine triphosphate, and NADPH stands for nicotine adenine dinucleotide phosphate. These two substances are both unstable forms of energy which the plant then uses for other reactions. During a chemical reaction, water molecule gets splits and release oxygen into the air.

What is Chemosynthesis?

Chemosynthesis is another process which provides fuel to live on earth. In some environments, primary production of fuel occurs through chemosynthesis (a nutrition characteristic) which runs on chemical energy. Chemosynthesis is a process of use of energy produced by inorganic chemical reactions to produce food. This process occurs in the heart of deep sea communities, sustaining life in the absolute darkness where the light of the sun does not penetrate. All organisms doing chemosynthesis use the energy released by chemical reactions to make sugar. Different species use different pathways for chemosynthesis. For example, undersea hot springs are the most extensive ecosystem which based on chemosynthesis. At these hydrothermal vents, bacteria oxidize hydrogen sulfide, add carbon dioxide and oxygen and produce water, sulfur, and sugar. Other bacteria produce sugar matter by reducing sulfide or oxidizing methane. Chemosynthetic bacteria are present in hot springs on land and on the seafloor around hydrothermal vents, whale carcasses, cold seeps and sunken ships. Hydrogen bacteria are most numerous group of chemosynthetic bacteria.

Photosynthesis vs. Chemosynthesis

  • Both photosynthesis and chemosynthesis need carbon dioxide as fuel for the process to produce carbohydrates.
  • Both processes result in energy source for the organisms.
  • Photosynthesis occurs only in green plants or in organisms which have chlorophyll while chemosynthesis occurs only in bacteria.
  • Photosynthesis needs sun energy as an essential requirement while chemosynthesis does not need solar energy for the process.
  • Photosynthesis also needs oxygen for the process while chemosynthesis does not need oxygen for the process.
  • Water is used during the process of photosynthesis while water is produced as the end product in chemosynthesis.
  • Photosynthesis provides significant contribution of energy to the total biosphere energy reserve while chemosynthesis shows no such contribution.

Video Explanation

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White

Types of Growth that Take Place in Bacteria

Diauxic growth is a diphasic growth represented by two growth curves intervened by a short lag phase produced by an organism utilizing two different substrates, one of which is glucose. When E. coli grows in a medium containing both glucose and lactose, it uses glucose preferentially until the glucose is exhausted.

Then after a short lag phase during which bacterium synthesizes the enzymes needed for lactose use, growth resumes with lactose as a carbon source. If this diphasic growth of E. coli is plotted in respect to bacterial density against time, two growth curves follow one after the other intervened by a short lag phase to produce a diauxic or diphasic growth curve (Fig. 19.3).

The enzyme needed for lactose use is β-galactosidase, which splits lactose into glucose and galactose, and the bacterium utilizes glucose for growth. Galactose can also be utilized, but only after it is converted to glucose. It has been demonstrated that E. coli growing in a medium containing both glucose and galactose produces a diauxic (diphasic) growth curve as in case of glucose and lactose.

Similar response has been found in case of other sugars such as arabinose, maltose, sorbitol, etc. when they are used in combination with glucose by E. coli. Each of these sugars is utilized only after glucose has been used up in the growth medium.

The cause of diauxic (diphasic) growth is complex and not completely understood, it is considered that catabolite repression or the glucose effect probably plays a part in it. In catabolite repression of the lac-operon of E. coli, glucose exerts an inhibitory effect on the transcription of the lac genes.

As a result, lactose- utilization enzymes are not synthesized, even if lactose is present in the medium. When glucose is completely consumed by E. coli, the bacterium is now competent to transcribe the lac-operon genes resulting in production of necessary enzymes that help metabolise lactose.

Type # 2. Synchronous Growth:

Synchronous growth of a bacterial population is that during which all bacterial cells of the population are physiologically identical and in the same stage of cell division cycle at a given time. Synchronous growth helps studying particular stages or the cell division cycle and their interrelations.

In most of the bacterial cultures the stages of growth and cell division cycle are completely random and thus it becomes difficult to understand the properties during the course of division cycle using such cultures. To overcome this problem, the microbiologists have developed synchronous culture techniques to find synchronous growth of bacterial population.

Synchronous culture is that in which the growth is synchronous i.e. all the bacterial cells of the population are physiologically identical and in the same stage of cell division cycle at a given time.

A synchronous culture can be obtained either by manipulating environmental conditions such as by repeatedly changing the temperature or by adding fresh nutrients to cultures as soon as they enter the stationary phase, or by physical separation of cells by centrifugation or filtration.

An excellent and most widely used method to obtain synchronous cultures is the Helmstetter-Cummings Technique (Fig. 19.4) in which an unsynchronized bacterial culture is filtered through cellulose nitrate membrane filter.

The loosely bound bacterial cells are washed from the filter, leaving some cells tightly associated with the filter. The filter is now inverted and fresh medium is allowed to flow through it.

New bacterial cells, that are produced by cell division and are not lightly associated with the filter, are washed into the effluent. Hence, all cells in the effluent are newly formed and are, therefore at the same stage of growth and division cycle. The effluent thus represents a synchronous culture.

Type # 3. Continuous Growth: Chemo- Stat and Turbidostat:

Contrary to the studies in batch culture where the exponential growth of bacterial population is restricted only for a few generations, it is often desirable to maintain prolonged exponential growth of bacterial population for genetical and biochemical studies, and in industrial processes.

This condition is obtained by growing bacteria in a continuous culture, a culture in which nutrients arc supplied and end products continuously removed.

A continuous culture, therefore, is that in which the exponential growth phase of bacterial population can be maintained at a constant rate (steady state growth) for over a long period of time by continuously supplying fresh medium from a reservoir to growth chamber and continuously removing excess volume of culture medium of growth chamber through a siphon overflow.

By doing so the microbes never reach stationary phase because the end products do not accumulate to work as inhibitory to growth and nutrients arc not completely expended.

Continuous culture systems can be operated as chemostats or as turbidostats. In a chemostat (Fig. 19.5) the flow rate is set at a particular value with the help of a flow rate regulator and the rate of growth of the culture adjusts to this flow rate. That is, the sterile medium is fed into the vessel at the same rate as the media containing microorganisms is removed.

In a turbidostat (Fig. 19.6), the system includes an optical sensing device (photoelectric device) which continuously monitors the culture density in the growth vessel and controls the dilution rate to maintain the culture density at a constant rate. If the culture density becomes too high the dilution rate is increased, and if it becomes too low the dilution rate is decreased.

The turbidostat differs from the chemostat in many ways. The dilution rate in a turbidostat varies rather than remaining constant, and its culture medium lacks a limiting nutrient. The turbidostat operates best at high dilution rates the chemostat is most stable and effective at low dilution rates.

Are the bacteria doing the same photosynthesis as plants do? - Biology

32) Which part of a cell allows nutrients and other materials to enter and leave the cell?

c) chloroplast d) cell membrane

10) What separates living organisms from nonliving things?

Living things have all 5 MR. RUG characteristics.

11) What is the basic unit of all living organisms?

The basic unit of all living organisms is cells.

20 One important difference between living things and nonliving things is that only living things have

Which two organisms above belong to the same kingdom? [1]

27 What is the outermost structure in a plant cell?

(1) cell membrane (3) cell wall

(2) cytoplasm (4) chloroplast

15 In multicellular organisms, cell division is

(2) locomotion (4) respiration

25 Which group is made up of organisms that are all members of the same kingdom?

(1) cat, frog, and mushroom (2) mold, bacteria, and apple tree

(3) grass, worm, and shark (4) fern, rose bush, and corn plant

34 In a one-celled organism, cell division is responsible for

(4) production of sex cells

41 Which illustration is an example of a multicellular organism?

3) When a single-celled organism reproduces asexually, the two resulting daughter cells will have

a) the same amount of genetic material as the parent cell

b) half as much genetic material as the parent cell

c) twice as much genetic material as the parent cell

d) different amount of genetic material depending upon the size of the cell

17 Some one-celled organisms can reproduce by

(1) hormone secretion (3) fertilization

(2) metamorphosis (4) cell division

39 A new yeast cell is sometimes produced from a single parent by a process called budding. The process of budding is best described as

(1) sexual reproduction, with genetically identical offspring

(2) sexual reproduction, with genetically different offspring

(3) asexual reproduction, with genetically identical offspring

(4) asexual reproduction, with genetically different offspring

8) What are the two products of photosynthesis?

a) carbon dioxide and oxygen

b) sugar and carbon dioxide

d) water and carbon dioxide

47 The diagrams in the first column of the chart below show various forms of reproduction. In the second column, circle the form of reproduction (asexual or sexual) shown by each of the diagrams.

Sexual (for the sperm and egg)

22 Which process produces oxygen that is released into the atmosphere?

(1) respiration (3) excretion

(2) locomotion ( 4) photosynthesis

18) Why do animals need plants?

The most important answers that I am looking for is that animals eat plants for their sugar and animals use the oxygen that plants produce.

13) Why do plants have chlorophyll?

Plants have chlorophyll to do photosynthesis. The do photosynthesis to make their own food, which is sugar.

52 Select one structure labeled in the plant system to the left and explain how it contributes to the way the organism functions.

Explanation: Use water, sunlight and CO2 to make sugar (by doing photosynthesis).

Explanation: Collect water for the leaves to do photosynthesis.

Explanation: Transport water and sugar around the plant.

41) What can the maple tree do that the beetle cannot do?

b) move from place to place

d) take in oxygen to burn food for energy

10 The female sex cell is the

27) What is pollen and where is it stored in a flower?

Pollen carries sperm cells. It is located on the stamen, which are the little hammer-looking things sticking out of flowers.

Watch the video: 2 1 Η παραγωγή θρεπτικών ουσιών στα φυτά Η φωτοσύνθεση (July 2022).


  1. Kit

    as you would read carefully, but you have not understood

  2. Notus

    Very interesting, but in the future I would like to know more about this. I liked your article very much!

  3. Wselfwulf

    Agree, this is the excellent idea

Write a message