Chapter 11: The diversity of Prokaryotic Organisms
Endospore-formers
Bacillus and clostridium species, most common gram-posiive rod-shaped bacteria that form endospores. Bacillus species include obligate aerobes and facultative anaerobes. B anthracis causes anthrax
Filamentous sulfur oxidizers
Beggiatoa and thiothrix species. Live in sulfur springs, seqage poluuted waters and on the surface of marine and freshwater sediments. Store sulfur and deposit it as intracellular granules. Beggiatoa filaments move by gliding, while the thiothrix filaments are immobile
Heliobacterium
Anoxygenic phototroph that has not been extensively studied. Gram-positive endospore forming rods related to members of the genus clostridium
Anoxic
Devoid of O₂
Coliforms
Enteric bacteria that characteristically ferment lactose
Methane-generating hyperthermophiles
Extreme thermophiles, Methanothermus species can grow in temperatures as high as 97°C and grow optimally at 84°C oxidize H₂ using O₂ as a terminal electron acceptor to yield methane.
Green bacteria
Gram-negative anoxygenic organisms, typically green or brownish in color.
Purple bacteria
Gram-negative anoxygenic phototroph. Appear red, orange, or purple due to their light-harvesting pigments. The components of their photosynthetic apparatus are contained within the cytoplasmic membrane
Prosthecate bacteria
Gram-negative bacteria that have projections called prosthecae, which are extensions of the cytoplasm and cell wall. They provide increased surface are to facilitate absorption of nutrients. SOme allow the organisms to attach to solid surfaces
Nitrifiers
Gram-negative bacteria that obtain energy by oxidizing inorganic nitrogen compounds such as ammonia or nitrite.Concern farmers that fertilize with ammonium nitrogen, nitrifiers make it less potent.They consume O₂ as they oxidize nitrogen compounds. Two groups, ammonia oxidizers: include the genera nitrosomonas and nitrosococcus, convert ammonia to nitrite; Nitrite oxidizers: include the genera nitrobacter, convert nitrite to nitrate
The genus spirillum
Gram-negative spiral-shaped, microaerophilic bacteria. Spirillum volutans forms volutin granules, which are storage forms of phosphate sometimes called metachromatic granules to reflect their characteristic staining with the dye methylene blue. Cells are typically large and an be seen in wet mounts moving to a narrow zone near the edge of the coverslip, where O₂ is available in the optimum amount
Hydrogen-oxidizing bacteria
Gram-negative. Genera include aquifex and hydrogenobacter. Obligate chemolithotrophs. thermophilic, typically inhabit hot springs.
The genus micrococcus
Gram-positive cocci found in soil and on dust particles, inanimate objects, and skin. Often airborne and can easily contaminate bacteriological media. Typically form pigmented colonies. Include M. luteus. Tolerate dry conditions and can grow in salty environments
The genus propionibacterium
Gram-positive pleomorphic (irregular shaped) rods that produce propionic acid as their fermentation end product. Can also ferment lactic acid. Their end products are important in swiss cheese production. The propionic acid gives the cheese its flavor and the CO₂ creates the holes. Also found in the intestinal tract and in anaerobic environments on the skin
The genus mycoplasma
Lack a cell wall, flexible, can pass through the pores of filters that retain other bacteria. Have sterols in their membrane, providing added strength and rigidity, protecting the cells form osmotic lysis. Smallest forms of life, their genomes are thought to be the minimum size for encoding essential functions for a free-life organism. M. pneumoniae causes a form of pneumonia called "walking pneumonia," which cannot be treated by antibiotics that interfere with peptidoglycan synthesis because these organisms lack a cell wall. Mycoplasma growing on a solid media produce a "fried egg" appearance.
Chemotrophs
Organisms that harvest energy by oxidizing chemicals
Primary producers
Organisms that harvest the energy of sunlight and use it to convert CO₂ into organic compounds.
Chemoorganotrophs
Oxidize organic compounds such as glucose to obtain energy
Chemolithotrophs
Oxidize reduced inorganic chemicals such as hydrogen gas (H₂) to obtain energy
Oxygenic phototrophs
Photosynthetic organisms that use water as a source of electrons for reducing power
Facultative anaerobes
Preferentially use aerobic respiration if O₂ is available, but can ferment
The genera thermus and deinococccus
Related genera. Thermus are thermophilic and have heat-stable enzymes, have an unusual cell wall and are gram-negative. Deinococcus unusual cell wall has multiple layers and are gram-positive. Are extraordinarily resistant to gamma radiation. It's genome can be shattered into many fragments, yet its enzymes can repair the extensive damage.
The genus bacteroides
Small, strictly anaerobic, gram-negative rods and coccobacilli. Inhabit the mouth, intestinal tract and genital tract of humans and other animals. bacteroides fragilis and related species make up a third of the bacteria of human feces and are responsible for abscesses and bloodstream infections that follow appendicitis and abdominal surgery. Many are killed by brief exposure to O₂.
Sulfur-oxidizing, nitrate-reducing marine bacteria
Some marine bacteria. Store both sulfur (energy source) and nitrate (terminal electron acceptor). This energy source and terminal electron acceptor do not coexist. Thioploca species cope with this by forming long sheaths within which cells shuttle between the sulfur-rich sediments and nitrate-rich waters, storing reserves of sulfur and nitrate. The cells of he huge bacterium Thiomargarita namibiensis ("sulfur pearl of nambia") are pearly white color due to globules of sulfur in their cytoplasm, they are not motile and rely on storms or other disturbances to bring them into contact with nitrate-rich waters.
heterocysts
Species of Anabaena isolate nirogenase from O₂ by confining the process of nitrogen fixation to these specialized thick walled-cells. Lack photosystem II and do not generate O₂
Ecophysiology
The study of physiological mechanisms prokaryotes use to thrive in terrestrial and aquatic environments
Thermophilic extreme acidophiles
Thermoplasma and picrophilus grow in extremely acidic, hot environments. Thermoplasma grow optimally at pH 2; T. acidophilum lyses at neutral pH. Originally isolated from a coal waste pile. Picrophilus tolerate even more acidic conditions, growing optimally at a pH below 1. Two species isolated in Japan inhabited acidic areas in regions that spew sulfurous gases.
Endoflagella
Unlike typical flagella, endoflagella are contained within the periplasm. The flagella extend toward each other, overlapping in the mid-region of the cell. Rotation of the endoflagella within the periplasm causes the cell to move like a corkscrew, sometimes deviating into flexing motions.
Fruiting body
When nutrients are exhausted myxobacteria begin to congregate and form one of these brightly colored complex structures. the cells inside the fruiting body differentiate to become spherical, dormant forms called microcysts that are considerably more resistant to heat, drying and radiation than vegetative myxobacteria cells but less resistant than bacterial endospores.
Sulfur- and sulfate-reducing bacteria
When sulfur compounds are used as terminal electron acceptors, they become reduced to form hydrogen sulfide, the compound responsible for the rotten egg smell of many anaerobic environments. Organic compounds (energy source) + S (electron acceptor) → CO₂ + H₂Sc
The genus mycobacterium
Widespread in nature and include harmless saprophytes, which live on dead and decaying matter, and pathogens. Stain poorly (waxy lipid in their cell wall). Pleomorphic rods; occur in chains that sometimes branch, or bunch together to form cordlike groups. M. tuberculosis causes tuberculosis, M. leprae causes leprosy (hansen's disease). More resistant to disinfectants than other vegetative bacteria. Resistant to common antimicrobial medications
Sheathed bacteria
form chains of cells encased within a tube, or sheath, helping the bacteria attach to solid objects located in favorable habitats while sheltering them from attack by predators. Masses of filamentous sheaths can be seen streaming from rocks in flowing water polluted by nutrient-rich wastes. interfere with sewage treatments by clogging pipes. Spread by forming motile "swarmer" cells that exit through the unattached end of the sheath. Then move to a new solid surface to attach. If enough nutrients are present they can multiply and form a new sheath. Include species of sphaerotilus and leptothrix which are gram-negative rods.
The genus staphylococcus
gram-positive cocci that are facultative anaerobes. Most, such as S. epidermidis, reside as harmless parts of the normal microbiota. Staphylococcus species are catalase-positive, distinguishing them from streptococcus, enterococcus and lactococcus, which are also gram-positive cocci but lack catalase. Staph aureus causes a variety of diseases, including skin and wound infections as well as food poisoining. Staph saprophyticus causes urinary tract infections
Ti plasmid
in A. tumefaciens a Ti plasmid (tumor inducing)
The genus streptomyces
more than 500 species of aerobic gram-positive bacteria that resemble fungi in their growth pattern.Form a mycelium (a visible mass of branching filaments called hyphae). Chains of characteristic spores called onidia develop at the tips of hyphae. These dormant spores are resistant to drying and are easily spread in air currents. Produce extracellular enzymes that allow them to degrade various organic compounds. Responsible for the "earthy" odor of soil. Produce geosmin. S. somaliensis, can cause an infection of subcutaneous tissue called an actinomycetoma. Produce a wide variety of medically useful antibiotics, including streptomycin, tetracycline and erythromycin.
Sulfur-reducing hyperthermophiles
obligate anaerobes that use sulfur as a terminal electron acceptor, generating H₂S. Harvest energy by oxidizing organic compounds and/or H₂. Found in sulfur hot springs and hydrothermal vents. Pyrolobus fumarii was isolated from a "black smoker", it grows between 90°C and 113°C. Pyrodictium occultum has an optimum temperature of about 105°C and cannot grow below 82°C. "strain 121" is the record holer for highest maximum growth temperature, uses iron as an electron acceptor.
Obligate aerobes
obtain energy using respiration exclusively; none can ferment
Aerobic chemoorganotrophs
oxidize organic compounds to obtain energy, using O₂ as the terminal electron acceptor
Extreme halophiles
require a minimum of 9% NaCl. thrive in 32% NaCl. aerobic or facultatively anaerobic chemoheterotrophs. Some can also obtain additional energy from light. Have the light-sensitive pigment bacteriorhodopsin, which absorbs energy from sunlight and uses it to expel protons from the cell. This creates a proton gradient that can be used to drive flagella or synthesize ATP. Include genera halobacterium, halorubrum, natronobacterium and natronococcus
The genera treponema and Borrelia
spirochetes that typically inhabit body fluids and mucous membranes of humans and other animals. Have a gram-negative cell wall, but are too thin to be viewed by conventional microscopy. Treponema are aobligate anaerobes or microaaerophiles that inhabit the mouth and genital tract. T. pallidum causes syphilis, has never been grown in a culture. Three borrelia species are pathogens, transmitted by arthropods such as ticks and lice, B. recurrentis and B. hermsii cause relapsing fever and B. burgdorferi causes Lyme disease. Borrelia species has a linear chromosome and many linear and circular plasmids
The genus Bdellovibrio
(bdello is greek for leech) Highly motile gram-negative curved rods that prey on E. coli and other gram-negative bacteria. It strikes its prey with enough force to propel the prey a short distance. It then attaches to its host and rotates with a spinning motion and makes digestive enzymes that break down lipids and peptidoglycan, eventually forming a hole in the cell wall of the prey. The bacterium then penetrates the peptidoglycan and lodges into the periplasm. There it degrades and utilizes the prey's cellular contents and derives energy aerobically oxidizing amino acids and acetate. It increases in length and divides to form several motile daughter cells. When the host cell lyses, the progeny are released to find new hosts and repeat the cycle.
Spirochetes
(greek spira for coil and chaete for hair) gram-negative bacteria that move through thick, viscous environments such as mud using a unique motility mechanism by means of endoflagella. Many are very slender and can be seen only by using special methods like darkfield microscopy. Many are difficult or impossible to grow in culture. INclude free-living species that inhabit aquatic environments and ones that reside on or in animals. Anaerobes or facultative anaerobes that thrive in muds and anaerobic waters. Leptospira are aerobic; L. interrogans causes leptospirosis, which can be transmitted in the urine of infected animals.
Methanogens
A group of archaea that generate ATP by oxidizing hydrogen gas, using CO₂ as a terminal electron acceptor producig methane. 4H₂ (energy source) + CO₂ (electrons acceptor) → CH₄ + 2H₂O. SOme can use alternative energy sources such as formate, methanol or acetate. Found in anaerobic environments where H₂ and CO₂ are both available. Include the genus methanospirillum and methanosarcina.
The genus agrobacterium
Gram-negative rod-shaped bacteria, have an unusual mechanism of gaining a competitive advantage in soil. Cause plant tumors by attaching to wounded plant tissue and transferring a portion of a plasmid to a plant cell. The transferrred DNA encodes the ability to synthesize plant growth hormones, causing uncontrolled growth of the plant tissue and resulting in a tumor. Also encodees for an unusual amino acid derivative, opine that can be used as a nutrient source for the agrobacterium.
Sulfur-oxidizing bacteria
Gram-negative rods or spirals, sometimes grow in filaments. Obtain energy by oxidizing elemental sulfur and reduced sulfur compounds. Aerobic chemolithotrophs.
The genus pseudomonas
Gram-negative rods that have polar flagella and produce pigments. Most are strict aerobes, some can grow anaerobically if nitrate is availabe as a terminal electron acceptor. Do not ferment, are oxidase-positive. Some can metabolize more than 80 different substrates.Play important roles in degradation of synthetic and natural compounds that resist breakdown by other organisms. Widespread, inhabit soil and water. Most are harmless, some cause disease in plants and animals. P. aeruginosa is a common opportunistic pathogen. Can grow in nutrient-poor environments and is resistant to disinfectants and antimicrobial infections.
Nanoarchaea
Nanoarcheota ("dwarf archaea"). Nanoarchaeum equitans grows as 400-nm spheres attached to the surface of-presumably parasitizing- ignicoccus species.
The genera chlamydia and chlamydophila
Quite different from other obligate intracellular parasites. Transmitted directly from person to person and have a unique growth cycle. Inside the host cell, they exist as infectious reticulate bodies, which reproduce by binary fission. Later the bacteria differentiate into smaller, dense-appearing infectious elementary bodies, which are released when the host cell ruptures. Their cell walls lack peptidoglycan but have other features of gram-negative cell walls. Chlamydia trachomatis causes eye infections and a sexually transmitted infection that mimics gonorrhea; chlamydophila pneumoniae causes atypical pneumonia; chlamydophila psittaci causes psittacosis, a form of pneumonia
The genera rickettsia, orientia, and ehrlichia
Responsible for several serious human diseases spread by blook-sucking arthropods such as ticks and lice. Rickettsia rickettsii causes rocky mountain spotted fever, R. prowazekii causes epidemic typuhs, O. tsutsugamushi causes scrub typhus, and E. chaffeensis causes human ehrlichiosis
The genus hyphomicrobium
Similar to caulobacter, except they have a distinct method of reproduction. The polar prostheca of the parent cell enlarges to form a bud. This continues enlarging and develops a flagellum, eventually giving rise to a motile daughter cell. The daughter cell (swarmer cell) then detaches and moves to a new location, eventually losing its flagellum and forming a polar prostheca at the opposite end to repeat the cycle.
Unicellular Sulfur oxidizers
Acidithiobacillus species. Terrestrial and aquatic habitats. Can bioleach, a process used to recover metals. They oxidize insoluble metal sulfides and produce sulfuric acids, lowering the pH converting the metal to a soluble form. Can be used to prevent acid rain. Can cause severe environmental problems such as producing sulfuric acid on exposed metal sulfides which can acidify nearby streams, and kill wildlife
myxobacteria
Aerobic gram-negative rods that have a unique developmental cycle as well as a resting stage. cells excrete a slime layer that other cells then follow, creating a swarm of cells in favorable conditions. When nutrients are exhausted the group behavior changes and they form fruiting bodies. Degraders of complex organic substances, can digest bacteria and aglgae and fungi. Include the genera chondromyces, myxococcus, and stigmatella
Coryneforms or diphtheroids
Bacteria that exhibit a characteristic morphology. Pleomorphic rods, often club-shaped and arranged to form v shapes. Including corynebacterium. (koryne is greek for club.)
The genera campylobacter and helicobacter
Campylobacter and helicobacter are curved gram-negative rods. MIcroaerophiles, require specific atmospheric conditions to grow in culture. Campylobacter jejuni causes diarrheal disease in humans. Lives in the intestinal tract of domestic animals, particularly poultry. Helicobacter pylori inhabits the stomach, can cause stomach and duodenal ulcers and has been linked to stomach cancer. It produces urease that breaks down urea to produce ammonia, neutralizing the acid in the cell's immediate surroundings helping it survive in the stomach.
Obligate intracellular parasites
Cannot reproduce outside a host cell. The host cell supplies them with a readily available source of compounds they would otherwise need to synthesize themselves. Bacterial examples include members of the genera rickettsia, orientia, ehrlichia, coxiella, chlamydia and wolbachia, all tiny gram-negative rods or coccobacilli.
Acid-fast
Cells that resist destaining, even with acidic decolorizing solutions. Mycobacterium
Nitrogen-fixing Cyanobacteria
Critical ecologically. Can incorporate N₂ and CO₂ into organic material that can be used by other organisms. Can support other life. Help limit atmospheric CO₂ buildup by using it as a carbon source.
The genus legionella
Found in aquatic environments, often reside within protozoa. Have been isolated from water in air conditioners and produce misters. Gram-negative obligate aerobes that use amino acids, not carbs as a source of carbon and energy. Legionella pneumophila can cause respiratory disease when inhaled in aerosolized droplets.
Cyanobacteria
Diverse group of more than 60 genera of gram-negative bacteria. Inhabit a wide range of environments, including freshwater and marine habitats, soils, and surfaces of rocks. Many are able to convert nitrogen gas (N₂) to ammonia, which can then be incorporated into cell material. Are morphologically diverse. Some are unicellular with typical prokaryotic shapes such as cocci, rods, and spirals, others are filamentous multicellular associations called trichomes that may or may not be enclosed within a sheath that holds and surrounds a chain of cells). motile trichomes glide as a unit. Cyanobacteria that inhabit aquatic environments often have gas vesicles, allowing them to move vertically within the water column. A large number of cyanobacteria is called a bloom. The buoyant cells lyse and decay in the summer, creating a foul-smelling scum. Their photosystems are like those contained within algae and plants. Also have phycobilliproteins that absorb energy from wavelengths not well absorbed by chlorophyll that contribute to the blue-green or sometimes reddish color of the bacteria. Some cyanobacteria produce geosmin, it has an earthy odor which makes water taste odd
The genus corynebacterium
Facultative anaerobes. Are widespread in nature. Gram-positive pleomorphic rods. Some are strict aerobes. C. diptheriae can cause the disease diphtheria
Filamentous anoxygenic phototrophic bacteria
Form multicellular arrangements and exhibit gliding motility. Have chlorosomes. Some preferentially use organic compounds to generate reducing power and can also grow in the dark aerobically using chemotrophic metabolism. Genera includes Chloroflexus
Green sulfur bacteria
Found in environments similar to purple sulfur bacteria. Use hydrogen sulfide as a source of electrons for reducing power and form sulfur granules. Their granules form on the outside, rather than the inside of the cell. Pigments are located in chlorosomes. Lack flagella but have gas vesicles. Strict anaerobes. Genera include Chlorobium an Pelodictyon
Purple non-sulfur bacteria
Found in moist soils, bogs and paddy fields. They preferentially use organic molecules rather than hydrogen sulfide as a source of reducing power. Lack gas vesicles. Grow as phototrophs using organic molecules, but many can use a metabolism similar to purple sulfur bacteria, employing hydrogen gas or hydrogen sulfide as an electron source. Most can grow aerobically in the absence of light using chemotrophic metabolism. Genera include Rhodobacter and Rhodopseudomonas
Extreme thermophiles
Found near volcanic vents and fissures that release sulfurous gases and other hot vapors that are similar to early earth's environment. Also found in hydrothermal vents in deep sea and hot springs.
Lactic acid bacteria
Gram positive bateria that produce lactic acid as a major end product of their fermentative metabolism. Includes streptococcus, enterococcus, lactococcus, lactobacillus and leuconostoc. Most can grow in aerobic environments, but they only ferment. Lack catalase.
The genus clostridium
Gram positive rods that can form endospores. Their endospores can tolerate O₂. Anaerobic chemoorganotroph-fermentation. Some species can ferment amino acids by oxidizing one amino acid, using another as a terminal electron acceptor
The genus neisseria
Gram-negative bacteria, typically kidney-bean-shaped cocci in pairs. common microbiota of animals including humans, growing on mucous membranes. Typically aerobes, but some can grow anaerobically if a suitable terminal electron acceptor such as nitrite is present. N. gonorrhoeae causes gonorrhea and N. meningitidis causes meningitis
The genus haemophilus
Gram-negative coccobacilli that are "blood loving." Require hematin and/or NAD, which are found in blood. Common microbiota of the respiratory tract. H. influenzae causes ear infections, respiratory infections and meningitis, primarily in children. Haemophilus ducreyi causes the sexually transmitted disease chancroid.
The genus azotobacter
Gram-negative pleomorphic, rod-shaped bacteria that live in soil. Can form a cyst (a type of resting cell that have negligible metabolic activity and can withstand drying and ultraviolet radiation but are not highly resistant to heat.). Can fix nitrogen in aerobic conditions, the azotobacter species consumes O₂ so rapidly that a low O₂ environment is maintained inside the cell, and a protein binds nitrogenase protecting nitrogenase from O₂.
Thizobia
Gram-negative rod-shaped bacteria that fix nitrogen adn form intimate relationships with legumes. Includes genera rhizobium,sinorhizobium, bradyrhizobium, mesorhizobium and azorhizobium. Live within cells in nodules formed on roots of plants. The plants synthesize the protein leghemoglobin, which controls the O₂ levels. The bacteria are able to fix nitrogen in the resulting microaerobic environment. Endosymbionts, organisms that provide a benefit to the cells in which they reside.
The family enterobacteriaceae
Gram-negative rods. most reside in the intestinal tract of humans and other animals (enteron is greek for intestine). Enterobacter, klebsiella, proteus and E. coli are part of the intestinal microbiota. Shigella, Salmonella enterica and some strains of E. coli can cause diarrheal disease. Salmonella enterica serotype typhi causes typhoid and Yersinia pestis causes bubonic and pneumonic forms of plague. Facultative anaerobes that fermetn glucose and generally have peritrichous flagella.
The genus bifidobacterium
Gram-positive, irregular, rod-shaped anaerobes that reside primarily in the intestinal tract of humans and other animals. Predominant members of the intestinal microbiota of breast-fed infants and are thought to provide a protective function by excluding disease-causing bacteria. Formula fed infants have this genus but in a lower concentration
Purple Sulfur Bacteria
Grow in ordered masses in sulfur-rich aquatic habitats. Relatively large, may have gas vesicles to move. Store sulfur in intracellular granules. Prefer hydrogen sulfide to generate reducing power. Most are strictly anaerobes and phototrophs but some can grow in the presence of light aerobically. Genera include chromatium, thiospirillum and thiodictyon
Nitrogen fixation
Process exclusively done by prokaryotes where nitrogen gas (N₂) is converted to ammonia, which can then be incorporated into cell material.
The genus coxiella
Only characterized species of coxiella, C. burnetii is an obligate intracellular bacterium that survives well outside the host cell. During its intracellular growth, it forms spore-like structures called small-cell variants (SCVs) that later allow it to survive in the environment. These structures, however, lack the resistance to heat and disinfectants that endospores have. They cause Q fever of humans, caused by inhaling bacteria shed from infected animals. A problem with pregnant animals because high numbers of the bacteria can be found in the placenta of infected animals
The genus caulobacter
Serve as a model for research on cellular differentiation. Entirely different events occur in an orderly fashion at opposite ends of the cell. Have a single polar prostheca , called a stalk. The tip of the stalk is an adhesive holdfast that helps it attach. To multiply, the cell elongates and divides by binary fission, producing a motile swarmer cell at the end opposite the stalk. The swarmer cell has a flagellum, located at the pole opposite the site of division. Swarm cell detaches and moves to a new location, where it adheres via a holdfast near the base of its flagellum. It loses its flagellum, replacing it with a stalk. Then the daughter cell can replicate its DNA and repeat the process. With each division, a ring remains at the site of division, allowing a researcher to count the number of progeny
Bioluminescent bacteria
Some species of photobacterium and vibrio can emit light. This helps other organisms such as camouflaging squid. Luminescence is catalyzed by luciferase, genes that encode this enzyme are expressed only when the density of the bacterial population reaches a critical point. Gram-negative rods with polar flagella. Facultative anaerobes and typically inhabit aqueous environments. Some vibrio species, V. cholerae and V. parahaemolyticus are pathogenic and neither is bioluminescent.
Magnetotactic bateria
Such as magnetospirillum (aquaspirillum) magnetotacticum contain a string of magnetic crystals that align cells with the earth's magnetism allowing them to move up or down in water or sediments. This unique type of movement allows them to locate the microaerophilic habitats they require. Gram-negative, spiral-shaped organisms
Sulfur oxidizers
Sulfolobus species are found at the surface of acidic sulfur-containig hot springs cuh as many of those found in yellowstone national park. Obligate aerobes that oxidize sulfur compounds, using O₂ as a terminal electron acceptor to generate sulfuric acid. Thermoacidophilic, only grow above 50°C and at a pH between 1 and 6
The genus wolbachia
The only known species of wolbachia, W. pipientis, infects arthropods and parasitic worms. Is transmitted maternally, via eggs of infected females to their offspring. In arthropods Bacterium uses unique strategies to increase overall population of infected females, including killing male embryos, allowing infected females to reproduce asexually and causing infecteed males to gain female traits. The parasite also destroys embryos resulting from the mating of an infected male with either an uninfected female or a female infected with a different strain. Does not infect mammals but it resides within filarial worms that cause the diseases river blindness and elephantiasis. The inflammation from these diseases results from the immune response against the bacterial cells in the invading worms.
Anoxygenic phototrophs
Use hydrogen sulfide or organic compounds as a source of electrons when making reducing power for biosynthesis, therefore do not generate O₂. Live in environments that have little or no O₂ yet light penetrates such as bogs, lakes and the upper layer of muds. Have bacteriochlorophyll, absorb wavelengths that penetrate deeper than those absorbed by clorophyll a.
