Bacterial Diversity Presentation

Prepared and Presented byDeepika Rana

1601M.Sc. Microbiology (I)

MDU,Rohtak

Thermophilic microbes are found in both the bacterial and archael domains, but to date, all hyperthermophilic prokaryotes(those with optimum growth temperature above 85°C) belong to the Archae. The phylum Aquificiae and Thermotoga are two best examples of bacterial thermophiles.

Aquifexand

Thermotoga

WHAT ARE THERMOPHILES?•A thermophile is an organism – a tyoe of extremophile- that thrives at relatively high temperature, between41 and 122°C(106 and 252°F). E.g.,Sulfolobus acidocaldarius, Thermus aquaticus.•Thermophilic eubacteria are suggested to have been amongst the earliest bacteria.•Thermophiles are found in various geothermally heated regions of the Earth, such as hot springs like those of Yellowstone National Park and deep sea hydrothermal vents as well as decaying plant matter, such as peat, bogs and compost.•Thermophiles contain enzymes that can function at high temperature.•Some of these enzymes are used in molecular biology, and in washing agents.•The G+C content levels was correlated with the temperature range condition.

Scientific Classification• Domain: Bacteria• Phylum: Aquificae• Class: Aquificae• Order: Aquificales• Family: Aquificaceae• Genus: Aquifex• Species: A. Aeolicus A. pyrophilus

Aquifex

Aquificae habitatWhite flocculent mats in and around the extremely gassy, high-temperature (>100°C, 212°F) white smokers at Champagne Vent.

• They are true bacteria as opposed to the other inhabitants of extreme environments, the Archaea.

• Aquifex pyrophilus is a gram-negative, microaerophilic rods.

• It is non-spore forming.• They are generally 2.0-6.0µm in length

and have a diameter of 0.4-0.5µm.• Like A. pyrophilus, A. aeolicus is

motile and possesses monopolar polytrichous flagella. More than25 genes encoding proteins involved in flagellar structure and biosynthesis have been identified in A.aeolicus.

Aquifex pyrophilus (ultrathin section).

Morphology

• As autotrophic organisms, Aquifex fir carbon di-oxide from the environment to get the carbon they need.

• They are chemolithotrophic which means that they draw energy for biosynthesis from inorganic chemical sources.

• The enzymes this organism uses for aerobic respiration are similar to those present in other aerobic bacteria.

• Non-N-methylated APT lipids can be observed as a common phospholipids head group in Aquifex.

METABOLISM

As an autotroph, A. aeolicus obtains all necessary carbon by fixing CO2 from the environment.

The reductive (reverse) TCA cycle fixes two molecules of CO2 to form acetyl-coenzyme A (acetyl-CoA) and other biosynthetic intermediates.

The A. aeolicus genome contains genes encoding malate dehydrogenase, fumarate hydratase, fumarate reductase, succinate-CoA ligase, ferredoxin oxidoreductase, isocitrate dehydrogenase, aconitase and citrate synthase, which together could constitute the TCA pathway.

The TCA cycle is vital as it provides the substrates of many biosynthetic pathways.

Reductive Tricarboxylic Acid Cycle

Growing autotrophically, A. aeolicus must synthesize pentose and hexose monosaccharides from products of the reductive TCA cycle. Pyruvate produced by pyruvate ferredoxin oxidoreductase or by pyruvate carboxylase (oxaloacetate decarboxylase) may enter the Embden–Meyerhof–Parnas pathway of glycolysis and gluconeogenesis.

Genes encoding fructose-1,6-bisphosphatase, an essential gluconeogenic enzyme in E. coli, have not been identified in the genomes of the autotrophs A. aeolicus or, suggesting that an unidentified pathway may exist.

The A. aeolicus genome also encodes enzymes of the pentose-phosphate pathway and enzymes for glycogen synthesis and catabolism.

The main enzymes involved in Entner- Duodroff Pathway are also absent.

Gluconeogenesis through theEmbden-Meyerhoff-Parnas Pathway

•Aquifex species are able to grow by using oxygen concentrations as low as 7.5 p.p.m. •The enzymes for oxygen respiration are similar to those of other bacteria: ubiquinol cytochromec oxidoreductase (bc 1 complex), cytochrome c (three different genes) and cytochrome c oxidase .•The physiological role of most of these oxidoreductases is unknown or ambiguous, but two deserve comment. There is a putative nitrate reductase in the genome, although A. aeolicus has not been observed to perform NO3

- respiration, unlike the closely related A. pyrophilus.

Respiration

OXIDATIVE STRESS•A. aeolicus grows optimally under microaerophilic conditions and consequently possesses various protective enzymes to counter reactive oxygen species, particularly superoxide and peroxide.

•The genome contains three genes encoding superoxide dismutases.

•No catalase genes were identified.

•There are several genes in the genome that might encode proteins that catalyze the detoxification of H2O 2, including cytochrome c peroxidase, thiol peroxidase, and two alkyl hydroperoxide reductase genes.

•All of these enzymes require an exogenous reductant and therefore do not evolve O2. However, treatment of A. pyrophilus or A. aeolicus biomass with H 2O2 results in the rapid evolution of gas bubbles.

Ecological significance• Aquifex are thermophilic and often grow underwater

volcanoes, thermal ocean vents, sulfur pools or hot springs.• It needs oxygen to carry on its metabolic machinery, but it can

function in relatively low levels of oxygen (A. pyrophilus can grow in levels of oxygen as low as 7.5 ppm).

• A.aeolicus and A.pyrophilus can grow at 95°C; they are one of the most thermophilic bacteria known.

• A.aeolicus was first obtained by R.Huber and K.F. Stetter at the Aeolic island (North of Sicily, Italy) whereas A.pyrophilus was obtained at the Kolbensey Ridge, North of Iceland.

Approximately 2 meters downstream of the spring pictured to the right. Pink microbial filaments containing Aquifex and Thermotoga were found in this channel. The tempurature was measured to be 83 degrees Celsius and the pH was found to be 8. From the Lunar and Planetary Institute.

Economic Importance• Hyperthermophilic bacteria such as Aquifex are

important for industrial purposes.• Its genes can be used in a variety of

biotechnological applications.

Thermotoga Scientific Classification Domain: BacteriaPhylum: ThermotogaeOrder: ThermotogalesFamily: ThermotogaceaeGenus: ThermotogaSpecies: T.elfii T.hypognae T.lettingae T.maritima T.napthophila T.neapolitana T.petrophila T.subterranea

Morphology • Thermotoga maritima is a non-sporulating, rod shaped, gram

negative bacterium.• When viewed under a microscope, it can be seen to encased in

a sheath-like envelope which resembles a toga, hence the "toga" in its name.

• The members of the phylum stain Gram-negative as they possess a thin peptidoglycan in between two lipid bilayers, both peculiar. The peptidoglycan is unusual as the crosslink is not only meso-diaminopimelate as occurs in Proteobacteria, but D-lysine.

• The species are anaerobes with varying degrees of oxygen tolerance. They are capable of reducing elemental sulphur (S0) to hydrogen sulphide, which in turn can be used.

• The CG (cytosine-guanine) content of T. maritima is 46.2%; most thermophiles in fact have high CG content; this has led to the speculation that CG content may be a non-essential consequence to thermophily and not the driver towards thermophily.

Outline of a Thermotoga maritima section showing the "toga".

• As an anaerobic fermentative chemoorganotrophic organism, T. maritima catabolizes sugars and polymers and produces carbon dioxide and hydrogen gas as by-products of fermentation.

• T. maritima is also capable of metabolizing cellulose as well as xylan, yielding H2 that could potentially be utilized as an alternative energy source to fossil fuels.

• Additionally, this species of bacteria is able to reduce Fe(III) to produce energy using anaerobic respiration.

• Collectively, these attributes indicate that T. maritima has become resourceful and capable of metabolizing a host of substances in order to carry out its life processes.

Metabolism

Ecological Significance• First discovered in the sediment of a marine

geothermal area near Volcano, Italy, Thermotoga maritima resides in hot springs as well as hydrothermal vents.

• Thermotoga species have been isolated from geothermally heated environments across the globe, including oil reservoirs, submarine hot springs, and continental sulfur springs

• The ideal environment for the organism is a water temperature of 80 °C (176 °F), though it is capable of growing in waters of 55–90 °C (131–194 °F).

• Thermotoga maritima is the only bacterium known to grow at this high a temperature; the only other organisms known to live in environments this extreme are members of the domain Archaea.

• The hyperthermophilic abilities of T. maritima, along with its deep lineage, suggests that it is potentially a very ancient organism.

Yellowstone National Park

Economic Importance• T. maritima’s xylanolytic abilities have attracted interest for food,

paper, and biofuel-related applications. • Xylooligosaccharides resulting from xylan degradation have been

shown to increase the numbers of beneficial gut bacteria, such as Bifidobacterium species.

• Their ability to degrade a wide range of simple and complex carbohydrates, produce fermentative hydrogen at high yield, and catalyze a variety of high-temperature reactions has been the basis for numerous biotechnological applications.

• These bacteria are also viewed as model systems for studying adaptation to high temperature and microbial evolution, as they present a challenge to conventional classification.

• A number of genome sequences for Thermotoga species have become available in the past few years , offering additional insights into the biology of these interesting bacteria and suggesting biotechnological opportunities.

References 1. Prescott’s Microbiology 7th edition Wiley et al2. www.els.net 3. mcmanuslab.ucsf.edu 4. Britannica 5. Google images6. Wikipedia

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