Prokaryotic Habitats and Importance

• Prokaryotes are ubiquitous and can be found everywhere, such as in hot springs, the Antarctic ice shield, and under extreme pressure two miles underwater.
• Prokaryotes are abundant on and in the human body.
• Bacteria thrive in the human mouth, nasal cavity, throat, ears, gastrointestinal tract, and vagina.
• Large colonies of bacteria are on healthy human skin, especially in moist areas like armpits and behind ears.
• Halophiles, a type of prokaryote, thrive in the Dead Sea's salty environments.
• Halobacterium salinarum is an archaeon and a halophile that lives in the Dead Sea.
• Shewanella can survive with minimal oxygen diffused by attaching to the sea floor using "nano cables" to sense oxygen.
• Prokaryotes capture (or "fix") and recycle crucial elements for life, like carbon and nitrogen.
• Animals rely on prokaryotes to convert carbon dioxide into usable organic carbon products via carbon fixation.
• Plants and animals rely on prokaryotes for nitrogen fixation, converting atmospheric nitrogen into ammonia.
• Ammonia is a compound plants use to form many biomolecules necessary for survival.
• Nitrogen-fixing bacteria such as Rhizobium living in the root nodules of legumes such as clover.

Bioremediation and Pathogens

• Prokaryotes aid the environment through bioremediation.
• Less than 1% of prokaryotes (bacteria) are human pathogens, but they collectively cause many human diseases.
• Prokaryotes exist in communities of interacting organism populations.
• A population constitutes individual organisms of the same species limited to a geographic area.
• Populations can have cooperative interactions that are beneficial, or competitive interactions where they compete for resources.
• The study of interactions between populations is microbial ecology.

Symbiosis

• Any interaction between different species in a community is symbiosis.
• Symbiotic relationships can be beneficial, harmful, or neutral regarding the species involved.
• Mutualism occurs when two interacting species both benefit from each other.
• Amensalism: one population is harmed whereas the other remains unaffected.
• Commensalism is where one organism benefits while the other is unaffected.
• Neutralism occurs when symbiotic organisms are unaffected in any way.
• Parasitism involves one organism that benefits while harming the other.

Microbiome

• A microbiome consists of prokaryotic and eukaryotic microorganisms like bacteria, fungi, viruses, and their genes that live on and inside us.
• Resident microbiota constantly live in or on our bodies.
• Transient microbiota are microorganisms only temporarily found in the human body.
• The Manual in Determinative Bacteriology summarizes kinds of bacteria known then using Latin binomial classification with morphological, physiological, and biochemical properties.
• Bergey’s Manual of Systematic Bacteriology contains many additional species and up-to-date descriptions of the taxonomy and biological properties of named prokaryotic taxa.
• Gram-negative and gram-positive bacteria are further classified.
• Deeply branching bacteria is a special group based on physiological, biochemical, and genetic features.
• Gram-negative bacteria further classified as Proteobacteria, Cytophaga-Flavobacterium-Bacteroides (CFB) and Spirochetes.
• Gram-positive bacteria are also classified regarding guanine and cytosine nucleotides.
• Gram-positive bacteria has less than 50% guanine and cytosine nucleotides.
• High G+C Gram-positive have more than 50% guanine and cytosine nucleotides.

Proteobacteria Phylum

• The American microbiologist Carl Woese suggested that "purple bacteria and their relatives" should be defined as a separate phylum that is now bacteria based on the similarity of the nucleotide sequences in their genome.
• Gram-negative Proteobacteria are divided into five classes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, and Epsilonproteobacteria.
• Alphaproteobacteria are obligotrophs, or organisms living in low-nutrient environments like deep oceanic sediments or glacial ice.
• Some Alphaproteobacteria, like Chlamydia and Rickettsia, are obligate intracellular pathogens and spend part of their lives inside host cells.
• Chlamydia and Rickettsia are metabolically inactive outside of a host cell.
• They cannot synthesize their own adenosine triphosphate (ATP), so they rely on host cells for their energy needs.
• Rickettsia spp. include many serious human pathogens.
  • R. rickettsii causes Rocky Mountain spotted fever.
  • R. prowazekii causes epidemic typhus.
  • R. typhi causes endemic typhus.
• Chlamydia are resistant to cellular defenses and can spread rapidly via elementary bodies.
• Elementary bodies are the metabolically and reproductively inactive endospore-like form that enter an epithelial cell.

Alphaproteobacteria Characteristics

• Agrobacterium tumefaciens is a plant pathogen that causes tumors in plants
• Bartonella is a facultative intracellular bacteria that causes trench fever and in humans from lice and fleas
• Brucella is a Facultative intracellular bacterium that causes brucellosis in cattle and humans from consumption of contaminated milk.
• Caulobacter: used in studies on cellular adaptation and differentiation.
• Coxiella: an obligatory intracellular bacterium that causes Q fever. . Ehrlichia: an obligatory intracellular bacterium that causes ehrlichiosis
• Hyphomicrobium: similar to Caulobacter
• Methylocystis: nitrogen-fixing aerobic bacteria.
• Rhizobium: nitrogen-fixing bacteria that live in soil with symbiotic relationships
• Rickettsia: obligate intracellular bacteria transmitted by ticks.

Betaproteobacteria

• Betaproteobacteria are eutrophs (or copiotrophs) and need copious organic nutrients.
• They can grow between aerobic and anaerobic areas.
• Genera include species of human pathogens.

Betaproteobacteria Table

• The genus *Bordetella pertussis * is aerobic and very fastidious and causes pertussis (whooping cough).
• The genus Burkholderia is aerobic and aquatic, and can cause diseases in horses and humans while being agents of nosocomial infections.
• The genus Leptothrix oxidize iron and manganese while being aquatic.
• Neisseria Gonorrhoeae requires a high moisture and carbon dioxide concentration and is oxidase positive on gonorrhea.
• Thiobacillus is thermophilic and acidophilic to oxidise sulphur aerobically

Gammaproteobacteria

• Gammaproteobacteria is the most diverse class of gram-negative bacteria incorporating human organisms.
• The family Pseudomonaceae includes the genus Pseudomonas.
• Pseudomonas aeruginosa:strictly aerobic and nonfermenting and able to create biofilms. These infect burns and is resisted to antibiotics.
• The family Pasteurellaceae includes several clinically relevant human/ animal pathogens. -Haemophilus influenzae can cause both upper and lower respiratory tract and does not affect influenza. -H. ducreyi can cause STI genital ulcers.
• The order Vibrionales includes the human pathogen Vibrio cholerae. -V. cholerae is is comma shaped bacterium that leads to watery diarreah -V. parahaemolyticus is a cause of gastrointestinal disease in human beings. -Another one is Aliivibrio fischeries which have symbiotic relations with squid..
• legionella pneumophilia can be from warm water in a tank.

Gammaproteobacteria Genera

• Beggiatoa is a Gram-negative bacteria; disc-shaped or cylindrical live in sewage treatment
• Enterobacter which is a gram negative is located in a urinary tract
• Erwinia a gram negative bacilli is found in leaft spots.
• Escherichia inhabits GI tract
• Hemophilus: is an anerobe that can grow
• Klebsiella is found in a pnumonia

Gammaproteobacteria

• Legionellais located in aquatics L. pneumophila
• Methylomonas is a methane source
• Pseudomonas is aerobic and causes wound infections/ hospital required infections in cysticfibers

Additional Gammaproteobacteria details

• Enterobacteriaceae are enteric (intestinal) bacteria.
• They are facultative anaerobes that ferment carbohydrates
• Coliforms can ferment lactose completely with acid and gas creation, Escherichia coli.
• Noncoliforms either cannot ferment lactose or do so incompletely with Salmonella spp & Yersinia pestis.
• Escherichia coli was found to be first in 1886 and most E-coli strands are in mutualistion relationships. However, the strands can also lead to cellular death.
• The genus Salmonella are of same bacteria.
• Some salmonella can lead symptoms of fever
• Figure Salmonella typhi is the agent used to caused typhoid.

Gammaproteobacteria Genus Continued

• Vibrato* inhibits seawater-flagellated and produces secretion in electrolyte tract. However, it also has species that are wound infections

Prokaryotes are widespread, thriving in diverse environments from hot springs to the human body. They're crucial for capturing and recycling elements like carbon and nitrogen, essential for life. Animals rely on prokaryotes to convert carbon dioxide into usable organic carbon.