Microbiology Exam 3

Hosts of viruses

• eukaryotic organisms

  • plants

  • animals

  • protists

  • fungi

Nucleocapsid

Capsid surrounding nucleic acid (either DNA or RNA)

Capsid

Protein coat

Enveloped Virus

Virus with a lipid membrane

Naked Virus

Virus without a lipid membrane

Helical Capsid

Shaped like a hollow tube with protein walls, size influenced by protomers and viral genome

Icosahedral Capsid

Made up of 5-6 protomers which make up capsomers. Polyhedron shaped

Complex Symmetry

Has neither icosahedral or helical capsids

dsDNA

Double-stranded DNA

ssDNA

Single-stranded DNA

dsRNA

Double-stranded RNA

ssRNA

Single-stranded RNA

Steps of Viral Life Cycle

1. Attachment

2. Entry of viral nucleocapsid

3. Synthesis of viral proteins and nucleic acids

4. Self-assembly of virions

5. Release of progeny virions

Cell lysis

Punctures the host plasma membrane, allowing the release of progeny. Common in bacterial viruses and some nonenveloped animal viruses.

Budding

Nucleocapsid is released from the membrane with envelope derived from host cell membrane.

Lytic Cycle

Virion reproduced and host cell is lysed, this can only occur once.

Lysogenic Cycle

Virus incorporates it’s genome into the host’s, allowing it to be replicated as the host’s genome is replicated. Continuous reproduction of virus.

Cytocidal Infection

An infection that results in cell death

Cytopathic infection

Virus hijacks host cell and causes changes

Plaque-Forming Unit

Unit of measurement, usually represents a single infectious virion.

Plaque

A clear area in a “lawn” of host cells that results from their lysis by a viral infection.

Viriods

Infectious agents made up of only RNA that cause plant diseases

Prions

Infectious particles only made up of proteins

Prion-Disease Symptoms

Progressive degeneration of the brain and eventual death

Prion Diseases

• Creutzfeldt-Jakob Disease

• Fatal Familial Insomnia

Common Archaea Habitats

• Hypersaline environments

• Marine communities

• Soil communities

• Extreme environments

• Human microbiome

Wood-Ljungdahl Pathway

• Creates Acetyl-CoA from CO₂

• Anaerobic

• Consumes 1 ATP per pyruvate produced

• 2 CO₂ → 1 Acetyl-CoA

HP/HB Pathway

• Creates pyruvate from CO₂

• Aerobic

• Consumes 9 ATP per pyruvate produced

• catalyzed by acetyl-CoA, CO₂ → 1 pyruvate

DC/HB Pathway

• Creates pyruvate from CO₂

• Anaerobic

• Consumes 5 ATP per pyruvate produced

• CO₂ + HCO₃ → 1 pyruvate

Thermoproteota Habitats

• Geothermal heated waters

• Soils that contain elemental sulfur

• Solfataras

N. equitans and I. hospitalis Symbiotic Relationship

• I. hospitalis greatly helps N. equitans by providing it with needed nutrients

  • N. equitans has really small genome

Mixotrophic

Utilizing the oxidation of ammonia to nitrite using oxygen as terminal electron acceptor to capture energy

What does Nitrosphaeria oxidize to create energy?

It oxidizes ammonia

Nitrosphaeria Characteristics

• Mixotrophic

• Hyperthermophile

Methanogenesis

• Last step in anaerobic degradation of organic compounds

• Generates methane from H₂ and CO₂

Haloarchaea Osmotic Stress

• Use Na⁺/H⁺ antiporters and K⁺ symporters to concentrate KCL and NaCl to levels similar to the environment

• Proteins in these microbes have hydrophobic amino acids which are acidic, allowing the proteins to maintain solubility

Halophile Habitat

• Dead Sea

• Great Salt Lake in Utah

Methanogen Habitat

• Wetlands

• Marshes

Thermatoga Cell Envelope

• Lacks lipopolysaccharides

• Enriched in Proteins

How do deinococci resist radiation?

They resist radiation with manganese complexes that neutralize reactive oxygen species

Deinococci Genome

• Polyploid

• Aerobic

• Heterotrophs

Oxygenic Photosynthesis

• Has Photosystems I and II

• Uses water as an electron donor

• Generates oxygen during photosynthesis

Anoxygenic Photosynthesis

• Utilizes inorganic electron donors such as hydrogen sulfide, sulfur and hydrogen

• Photoorganoheterotrophs

Chlorosome

Elongated, intramembranous vesicles found in the green sulfur and nonsulfur bacteria; they contain light-harvesting pigments.

• Has a lipid monolayer

Phycobilisomes

Protein complexes made up of phycobiliprotein pigments that absorb light for energy production

Phycocyanin

A blue phycobiliprotein pigment used to trap light energy during photosynthesis

• gives the bacteria it’s blue-green pigment

Phycoerythrin

A red photosynthetic phycobiliprotein pigment used to trap light energy

Obligate Intracellular Parasite

The organism must grow and reproduce within host cells, some may grow within their host without adverse effects, but many cause disease

Chlamydial Life Cycle Step 1

Elementary body attachment

Chlamydial Life Cycle Step 2

Host cell endocytoses the elementary body

Chlamydial Life Cycle Step 3

Differentiation of Elementary bodies into Reticulate bodies

Chlamydial Life Cycle Step 4

Reticulate bodies divide via budding

Chlamydial Life Cycle Step 5

Host DNA synthesis declines, reticulate bodies produce their own DNA, RNA and proteins

Chlamydial Life Cycle Step 6

Reticulate bodies located in an inclusion divide and decrease in size

Chlamydial Life Cycle Step 7

Reticulate bodies differentiate back into elementary bodies

Chlamydial Life Cycle Step 8

Infectivity increases and cell undergoes lysis

Chlamydial Life Cycle Step 9

Elementary bodies are released from host cell

How do humans host the genus Bacteroides?

They make up 30% of bacteria cultured from human feces. They aid in breaking down fiber.

Phylum Asgardarchaeota

• Contain eukaryotic signature proteins

• First species cultured in 2020

Phylum Nanoarchaeota

• Obligate symbionts

• Found in hot thermal vents

• Some of the smallest known organisms

• Very small genome

Phylum Thermoproteota

• Hyperthermophiles

• Live in hydrothermal vents and wells

• Mostly obligate anaerobes

  • Require sulfur

Phylum Nitrosphaeria

• Mesophilic ammonia oxidizers

• Contain thaumarchaeol (unique archaeal membrane protein)

• Found in a variety of environments

• Key to nitrogen cycle

Euyarchaeota

• Halophiles

• Methanogens

  • Produce methane

• Thermoplasmatales

Methanogens

• Obligate anaerobes

• Perform methanogenesis

Halophiles

• 8% or more salt

• Compatible solutes

• Acidic amino acids

Thermoplasms

• No cell walls, pleomorphic

• Thermophiles, acidophiles

• Unique cytoplasmic membranes

  • caldarchaeol

• Small genomes

Genus Aquifex

• Chemolithoautotrophs

  • capture energy by oxidizing hydrogen, thiosulfate, and sulfur with oxygen as terminal electron acceptor

Aquifex pyrophilus

• Microaerophilic rods

• Growth optimum at 85 - 95 degrees Celsius

Genus Thermatoga

• Rods with an outer sheathlike envelope

• Found in active geothermal areas and marine hydrothermal systems

  • terrestrial solfataric springs

• Chemoorganotrophs

Phylum Deinococci

• Spherical or rod-shaped, often seen in pairs or tetrads

• Non-motile

• Stain gram-positive

• Resistant to ionizing radiation and desiccation

Green Sulfur Bacteria

• Obligate anaerobic photolithoautotrophs

• Use H₂S, elemental sulfur, and H₂ as electron sources

• Elemental sulfur deposited outside cell

• Live in sulfide-rich areas

Phylum Cyanobacteria

• Largest and most diverse photosynthetic bacteria group

• Endosymbiotic cyanobacteria are thought to have evolved into chloroplasts

• Resembles photosynthesis of eukaryotes

  • Has photosystems I and II

  • Has chlorophyll a

  • Oxygenic photosynthesis

Phylum Spirochaetota

• Chemoorganotrophic bacteria with distinctive shape and motility

• Slender, long with flexible helical shape

• Periplasmic Flagella

• Rotation enables motility

  • Corkscrew-like movement

  • Flexing and crawling on solid surface

Periplasmic Flagella

Extend from both ends of the cylinder and wrap around the peptidoglycan

Where can Spirochetes be found?

• Hindguts of termites and wood-eating roaches

• Digestive tracts of mollusks and mammals

• Oral cavities of animals

What diseases is Spirochetes known for causing?

• Lyme disease

• Syphilis

Phylum Bacteroidota

• Includes photolithoautotrophic green sulfur bacteria and chemoheterotrophs

• Contribute to digestion of cellulose, agar, and chitin

• Common in terrestrial and marine environments, and in sewage treatment plants (contribute to process)

Genus Bacteroides

• Anaerobic and non-spore forming rods

  • Rarely motile

• Often found in human intestinal tract and animal rumens

• Benefit host by degrading cellulose, pectins and complex carbs

  • Constitute up to 30% of bacteria from human feces

  • Some cause disease

Phylum Fusobacteriota

• Spindle/football shaped

• Obligate of facultative anaerobes

• Inhabit both anoxic sediments and oral/intestinal habitats of mammals and insects

  • Can cause opportunistic infections in humans

Genus Bdellovibrio

• Aerobic, Gram-negative, curved rods with polar flagella

• Distinctive lifestyle— predatory

  • Preys on other diderm bacteria

  • Swims rapidly until it collides with prey and makes a hole in the host for entry

• Alternate between nonreplicating predatory phase and intracellular reproductive phase

Phylum Myxobacteria

• Gram-negative and aerobic soil bacteria

• Rods— slender or stout

• Gliding motility

• Life cycle includes fruiting bodies and spore formation

Genus Campylobacter

• C. jejuni causes gastroenteritis

• Some use molecular mimicy to cause the immune system to mistakenly attack the host’s nervous system

• Some non-pathogenic strains exist

Genus Helicobacter

• Helicobacter pylori

• Causes gastritis, peptic ulcer disease and gastric cancer

  • Burrows into the gastric mucosa to avoid acidity of stomach lumen as it cannot grow under pH of 4.5

  • Produces urease which drives the pH of stomach up

Phylum Proteobacteria

• Largest and most diverse

• All Gram negative

• Where most bacteria of significance are found

Class Alphaproteobacteria

• Protomitochondrion gave rise to eukaryotic mitochondria and related organelles through endosymbiosis

• Orders Rickettsiales and Protomitochondrion are apart of this class

  • Can live within arthropod and animal cells as mutualists or parasites

• Most are oligotrophs

• Metabolically diverse

  • Methylotrophy, chemolithotrophs, nitrogen fixers

Magnetotactic Bacteria

• Use intracellular magnets to align themselves with the Earth’s magnetic field

• Occupy freshwater or marine sediments

• Highly motile

• Genes encoding magnetosome proteins are clustered on genomic magnetosome island (GMI)

Order Rhizobiales

• Nitrogen fixing bacteria

• Pleomorphic under adverse conditions

• Grow symbiotically as nitrogen-fixing bacteroids within legume root nodules

  • led to success of leguminous plants

Pleomorphic

Ability to change an organism’s/cell’s shape or function in response to environmental stimuli

Order Rickettsiales

• Obligate intracellular bacteria

  • parasitic or mutualistic

• Grows in erythrocytes, macrophages, vascular endothelial cells

• Live in blood sucking arthropods— vectors or primary hosts

• Descended from free-living aerobic bacterium

What does the order Rickettsiales cause

• Typhus

• Rocky Mountain Spotted Fever

Class Gammaproteobacteria

• Largest class

• Half of Proteobacteria

• Contains many human pathogens

Burkholderia Cepacia

• Hospital acquired pathogen

  • commonly formed in lungs of cystic fibrosis patients

• Degrades more than 100 organic molecules and is active in recycling organic material

B. mallei

• Bioterrorism agent

Genus Neisseria

• Nonmotile, aerobic and gram-negative cocci

• Most often occur in pairs with adjacent sides flattened

  • May have capsules and pili

• Inhabitants of mucous membranes of mammals

What human pathogens come from the genus Neisseria?

• Neisseria gonorrhoeae — gonorrhea

• Neisseria meningitidis — bacterial meningitis

  • There is a vaccine against it

Genus Bordetella

• Aerobic coccobacilli chemoorganotrophs

  • Respiratory metabolism

  • Require organic sulfur and nitrogen (amino acids) for growth

• Mammalian parasites that multiply in respiratory epithelial cells

What does B. pertussis cause?

• Whooping cough

• Kennel cough

Genus Legionella

• Intracellular pathogen of protozoa

  • found in moist environments (cooling towers, AC, hot tubs)

• Transmitted through aerosolized water droplets

• Within host cell they are contained in Legionella-contain vacuole

  • Uses phagocytosis to it’s advantage

What does L pneumophila cause?

A causative pneumonia called Legionnaire’s disease

Genus Pseudomonas

• Opportunistic pathogens

• Straight or slightly curved rods

• P. aeruginosa

• Can degrade wide variety of organic molecules

• Heterogenous

• Motile (polar flagella)