BIO3310 – Chapter 10: Bacterial Diversity and Major Phyla

A comprehensive set of question-and-answer flashcards covering major bacterial phyla, Gram-stain distinctions, representative genera, pathogenic species, and ecological roles as presented in Chapter 10 of BIO3310.

What molecular marker is commonly used to build the bacterial phylogenetic tree?

16S rRNA gene sequences

Approximately how much do 16S rRNA sequences diverge every 50 million years?

About 1% (≈100 mutations per 1,000 nucleotides)

How many bacterial phyla have been cultured in the laboratory?

About 30 phyla

Microbiologists estimate the total number of bacterial phyla could exceed _.

1,000 additional phyla

Which seven ‘superphyla’ are most important for human health and the ecosystem?

Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes, Spirochaetes, Cyanobacteria, and Chlamydiae

What cell-wall feature distinguishes Gram-positive bacteria?

Thick peptidoglycan layer that retains crystal violet stain

Name the two major Gram-positive phyla.

Firmicutes and Actinobacteria

What is the G+C content characteristic of Firmicutes?

Low G+C content

Which Gram-positive phylum produces many antibiotics?

Actinobacteria

Which Gram-positive genus forms endospores and includes the anthrax agent?

Bacillus (e.g., Bacillus anthracis)

Which Gram-positive genus produces bulging spores and the neurotoxin Botox?

Clostridium (Clostridium botulinum)

Which non–spore-forming Gram-positive cocci are common skin microbiota?

Staphylococcus epidermidis

Which Gram-positive genus lacks a cell wall and has an ameboid shape?

Mycoplasma (a Mollicute)

Which dairy-fermenting Gram-positive rods are used to make yogurt?

Lactobacillus spp.

Which intracellular Gram-positive rod grows at refrigerator temperatures and causes food-borne illness?

Listeria monocytogenes

What distinguishes Actinomycetes within Actinobacteria?

They form branching mycelial filaments

Which Actinomycete genus is a major antibiotic producer?

Streptomyces

Which acid-fast Actinobacterium causes tuberculosis?

Mycobacterium tuberculosis

Which Actinobacterium causes diphtheria?

Corynebacterium diphtheriae

Which Actinobacterium is implicated in acne?

Cutibacterium acnes (formerly Propionibacterium acnes)

Species of Enterococcus, Streptococcus, and Staphylococcus can be distinguished in the lab by what test?

Patterns of hemolysis on blood agar

Which cell-wall lipid in Actinobacteria makes them acid-fast?

Mycolic acid

What structural trait is shared by all Proteobacteria?

Gram-negative cell envelope

Name three metabolic lifestyles found in Proteobacteria.

Heterotrophy, lithotrophy, and photosynthesis

Which Proteobacterial family contains facultative anaerobic enteric rods?

Enterobacteriaceae

Give an example of a commensal Enterobacteriaceae species.

Escherichia coli (non-pathogenic strains)

Which Enterobacteriaceae species causes plague?

Yersinia pestis

Which obligate aerobic Proteobacterium forms biofilms in cystic fibrosis lungs?

Pseudomonas aeruginosa

Which intracellular Proteobacterium causes Legionnaires’ disease?

Legionella pneumophila

What disease is caused by Neisseria gonorrhoeae?

Gonorrhea

What curved Proteobacterium survives stomach acid and causes gastritis?

Helicobacter pylori

Which Proteobacterium induces tumors in plants?

Agrobacterium tumefaciens

What nitrogen-fixing Proteobacterium forms root nodules on legumes?

Sinorhizobium meliloti (also Rhizobium/Bradyrhizobium)

Which predatory Proteobacterium invades the periplasm of other bacteria?

Bdellovibrio bacteriovorus

What group of Gram-negative rods are obligate anaerobes dominant in the human colon?

Bacteroides spp. (phylum Bacteroidetes)

Which molecules do Bacteroides spp. produce to modulate the host immune system?

Polysaccharide A and other communication molecules

What distinctive morphology defines Spirochaetes?

Tightly coiled spiral cells with periplasmic flagella beneath a sheath

Name the Spirochaete that causes Lyme disease.

Borrelia burgdorferi

Which phylum contains the only bacteria that release O₂ via photosynthesis?

Cyanobacteria

Besides fixing carbon, what key nutrient do many Cyanobacteria fix?

Nitrogen

What is unique about the cell walls of Chlamydiae compared with typical bacteria?

They have absent or highly reduced cell walls (yet are not mycoplasmas)

Chlamydia trachomatis infection can lead to which serious reproductive complication?

Pelvic inflammatory disease

Define “shelter species” in the context of pathogen evolution.

Organisms that harbor potential pathogens without direct human interaction, facilitating evolution of virulence traits

Endospore-forming bacilli with Gram-positive walls belong to which phylum?

Firmicutes

You discover an O₂-producing bacterium. To which phylum does it most likely belong?

Cyanobacteria

Which intracellular Proteobacteria cause Rocky Mountain spotted fever and Ehrlichiosis?

Rickettsia (R. rickettsii) and Ehrlichia species

Which Gram-negative diplococcus causes meningitis?

Neisseria meningitidis

Which Proteobacterium generates electricity through conductive nanowires?

Geobacter metallireducens

What lithotrophic Proteobacterium oxidizes nitrite in soil?

Nitrobacter winogradskyi

Which organism aggregates to form fruiting bodies in soil?

Myxococcus xanthus