Prokaryotic Microbiology: Proteobacteria, Extremophiles, and Archaea

What is the validly published name of Phylum Proteobacteria?

Pseudomonadota

How many classes are recognized in the Phylum Proteobacteria?

Six distinct classes

Name the classes of Phylum Proteobacteria.

Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria, Zetaproteobacteria

What type of organisms are included in the class Alphaproteobacteria?

Obligate and facultative intracellular parasites, as well as oligotrophs

What disease is caused by Rickettsia rickettsii?

Rocky Mountain Spotted Fever

How is Rickettsia rickettsii transmitted to humans?

Via tick bites

What is a characteristic of oligotrophs?

They can live in extremely low-nutrient environments

What is the significance of Pelagibacter ubique?

It is one of the most abundant bacteria on Earth, found in open ocean environments

What is the causative agent of Whooping Cough?

Bordetella pertussis

How does Bordetella pertussis cause disease?

It attaches to ciliated epithelial cells in the respiratory tract and releases exotoxins

What vaccine prevents Whooping Cough?

dTAP vaccine

What is the clinical impact of Bordetella pertussis in infants?

Approximately 50% of infant cases require hospitalization

What is a notable characteristic of Gammaproteobacteria?

They form the largest and most diverse class within Proteobacteria

What disease does Vibrio vulnificus cause?

Severe, necrotizing wound infections

What is the ecological role of Aliivibrio fischeri?

It forms mutualistic symbiotic relationships with marine animals

What is the function of gas vesicles in Cyanobacteria?

They regulate buoyancy within the water column

What do Cyanobacteria fix during the daytime?

Carbon dioxide (CO2) into organic carbon

What is the nighttime physiological process of Cyanobacteria?

Energy generation via fermentation or respiration of stored carbon

How do Cyanobacteria adapt to seasonal changes?

They alter their cell membrane lipid composition

What is a strategy Cyanobacteria use for UV protection?

They avoid permanent exposure at the surface to prevent DNA damage

What is the role of gas vesicles in low light conditions?

They enable cells to float upward toward light at the surface

What is the significance of the lux operon in Aliivibrio fischeri?

It regulates bioluminescence for counter-illumination camouflage

What are extremophiles?

Prokaryotes adapted to survival and growth in harsh physical or geochemical conditions.

What is a halophile?

An extremophile that thrives in elevated salt concentrations (0.3 M to 5.1 M NaCl).

What is a thermophile?

An extremophile that withstands or requires high temperatures (up to and exceeding 121 °C).

What is a psychrophile?

An extremophile that withstands or requires low temperatures (-20 °C to 10 °C).

What is an acidophile?

An extremophile that thrives in low pH environments (pH < 6).

What is an alkaliphile?

An extremophile that thrives in high pH environments (pH > 8).

What is a barophile (piezophile)?

An extremophile that thrives under high hydrostatic/atmospheric pressures, such as in deep ocean trenches.

What is a xerophile?

An extremophile that thrives in extremely dry conditions characterized by low water activity.

What are the two primary phyla of Gram-positive bacteria?

Phylum Actinobacteria (high G+C content) and Phylum Firmicutes (low G+C content).

What are the characteristics of Actinobacteria?

High genomic G/C content, Gram-positive morphology (short rods or branching filaments).

What is a representative genus of Actinobacteria?

Streptomyces spp., which produces over half of all clinically useful natural antibiotics.

What are the characteristics of Firmicutes?

Low genomic G/C content, Gram-positive morphology (typically rods or cocci), includes endospore formers.

What is an endospore?

A durable, non-reproductive structure formed by specific bacteria to protect their genetic material during unfavorable conditions.

What is the difference between a vegetative cell and an endospore?

A vegetative cell is metabolically active and undergoes normal growth, while an endospore is metabolically dormant and highly resistant.

What is sporulation?

The multi-stage developmental process of converting a vegetative cell into an endospore.

What is the purpose of the endospore stain?

To visualize endospores, which absorb malachite green and appear green inside or outside red/pink vegetative cells.

What is Bacillus anthracis?

A Gram-positive, rod-shaped, encapsulated, endospore-forming, aerobic zoonotic pathogen.

What are the forms of anthrax caused by Bacillus anthracis?

Cutaneous, inhalation, gastrointestinal, and injection anthrax.

What is Clostridium tetani?

A Gram-positive, rod-shaped, motile, obligate anaerobe, endospore-forming bacterium that causes tetanus.

How does Clostridium tetani cause disease?

Spores enter through deep puncture wounds and produce tetanospasmin, a neurotoxin causing spastic muscle contractions.

What is Clostridium botulinum?

A Gram-positive, rod-shaped, motile, obligate anaerobe, endospore-forming bacterium that produces the botulinum toxin.

What types of botulism are associated with Clostridium botulinum?

Foodborne, infant, wound, iatrogenic, and adult intestinal toxemia botulism.

What is the onset time for symptoms of foodborne botulism?

12 to 36 hours post-ingestion.

What is a major symptom of foodborne botulism?

Descending flaccid paralysis leading to respiratory failure.

What is the fatality rate for foodborne botulism?

5% - 10%.

What age group is primarily affected by infant botulism?

Infants under 6 months of age.

What are the symptoms of infant botulism?

Constipation, loss of appetite, systemic muscle weakness, loss of head control ('floppy baby syndrome').

What is the primary source of infant botulism?

Ingestion of bacterial spores from contaminated honey.

What distinguishes Domain Archaea from Bacteria?

Differences in membrane lipid structure, cell wall composition, and genetic machinery.

What is the former name of the phylum Methanobacteriota?

Euryarchaeota.

What type of organisms does the phylum Thermoproteota primarily include?

Aquatic, oceanic archaea; predominantly thermophiles, hyperthermophiles, acidophiles, and anaerobes.

What is the significance of the phylum Nanobdellota?

It comprises obligate symbionts.

What is the only described species in the phylum Microcaldota?

Microcaldus variisymbioticus.

What is the hypothesized ancestral lineage from which eukaryotic cells emerged?

Asgardarchaeota, part of the Promethearchaeota.

Where was Pyrolobus fumarii discovered?

On deep-sea hydrothermal vents ('Black Smokers').

What is the optimal growth temperature for Pyrolobus fumarii?

113 °C (235 °F).

What structural adaptation does Thermoproteus tenax possess?

A plasma membrane organized as a lipid monolayer.

What type of environment does Halobacterium salinarum thrive in?

Requires salinities greater than 4 M NaCl.

What is the optimal growth temperature for Methanopyrus kandleri?

98 °C.

Where is Methanobrevibacter ruminantium found?

Inside the rumen of ruminant livestock (cows).

What gas does Methanobrevibacter ruminantium produce?

Methane (CH₄) as a metabolic byproduct.

What role do Archaea play in human health?

They have complex structural and metabolic roles within human mucosal microbiomes.

What is methanogenesis?

A specialized form of anaerobic respiration where methanogenic archaea generate methane gas (CH₄).

What health implications are associated with Methanobrevibacter in the gut?

A reduction in methanogen populations is linked to malnutrition and colon cancer.

What is the pathogenic role of oral archaea in periodontal disease?

They contribute to disease states via mixed infections with sulfate-reducing bacteria (SRB).

What correlates with elevated levels of oral archaea in the human microbiome?

Tobacco smoking and obesity.