L4 nutrition and disease

Guild G bacteria are known as what?

Methanogenic bacteria

Methanogenic bacteria belong to which domain?

Archaea/archaebacteria

What process do guild G bacteria carry out?

Methanogenesis

Preferred substrates for methanogens?

CH4 and H2, can also use acetate

Methane formation equation from CO2 and H2?

CO2 + 4H2 → CH4 + 2H2O

Methane formation from acetate?

CH3COOH → CH4 + CO

Are guild G bacteria aerobic or anaerobic?

Obligate anaerobes

Typical genus name for methanogens?

Start with Methano

Methanotrophs utilize what as sole carbon source?

Methane

Methanotroph genus name?

Start with Methylo

Where do methanotrophs exist in environment?

Aerobic zone near anaerobic zone

Methanotrophy pathway?

CH4 → Methanol → Formaldehyde → Formate → CO2

Electron acceptor for methanotrophs?

O2

Electron acceptor for methanogens?

CO2

Which gases in flatulence are odourless and flammable?

CH4 and H2

Which gases in flatulence are odourless and non

flammable?

Why no purple/green sulphur bacteria in gut?

They need light

Why no methanotrophs in gut?

They need oxygen

What are VOCs?

Volatile organic compounds produced by bacteria

Examples of VOCs from bacteria?

Alkenes, alcohols, ketones, benzenoids, pyrazines, sulfides, terpenes

What can bacterial VOCs be used for?

Identify genera or contribute to human odour

What is an e

nose?

Define pathogen?

Organism causing disease by interfering with host functions

Define disease?

Pathological condition of organism with identifiable symptoms

Define infection?

Invasion and multiplication of pathogens in host tissues

Define pathogenicity?

Ability to cause disease

Define virulence?

Degree/intensity of pathogenicity

What is infective dose (ID)?

Number of cells needed to establish infection

Lower ID indicates what?

Higher virulence

ID of Vibrio cholerae?

10^3 to 10^8 cells

ID of Campylobacter jejuni?

~500 cells

ID of Shigella spp.?

~10 cells

Give examples of virulence factors on chromosome?

Capsule, endotoxin

Effect of virulence factors on bacterial growth?

Produce metabolic burden

Give examples of virulence factors on plasmids?

Toxins, enzymes, adhesins

Primary pathogens cause disease in whom?

Healthy individuals

Opportunistic pathogens cause disease when?

Host resistance is low

What is needed for pathogen invasion?

Reservoir, transmission, penetration of host barriers

Examples of natural reservoirs?

Soil, water, fomites, animals

Transmission by aerosols?

Coughing or sneezing

Transmission by direct contact?

Touch, sex, contaminated food, fomites

Transmission by vectors?

Fleas, lice, ticks

List natural barriers to infection?

Lysozymes, skin, mucus, cilia, acid, competition from commensals

Where do pathogens first interact after entry?

Mucosal surfaces

How do pathogens overcome flushing mechanisms?

Attach to surfaces and form biofilm

Skin damage can lead to infections by?

Opportunistic infections from pathobionts

Approximate number of bacteria in human body?

10^14

How do most bacteria live on the body?

Attached in biofilms

Why do pathogens struggle to colonize pre

existing biofilms?