Part 7: Normal Human Microbial Interactions Flashcards Preview

MBIO1010 > Part 7: Normal Human Microbial Interactions > Flashcards

Flashcards in Part 7: Normal Human Microbial Interactions Deck (65):
1

Human microbiome

The collection of all the microorganisms living in association with the human body

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Number of human cells in the human body

10^13

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Number of microorganisms in the human body

10^14

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Number of genes in the human genome

20,000

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Number of genes in the microbiome

20,000,000

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When does colonization begin?

After birth

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Where do microbiota live?

Every exposed area of the body i.e., skin and mucous membrane

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What area is free of microbes?

Internal tissues i.e., blood, muscles, organs

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How do microbiota contribute to health?

Produce beneficial products
Inhibit the growth of pathogens

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Benefit of Lactobacillus acidophilus

Protects the female reproductive tract

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Dry skin areas

Forearms, hands

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Dry skin has high numbers of

Betaproteobacteria

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Betaproteobacteria

Known from 16 rRNA genes
Rarely cultured

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Second highest bacteria on dry skin

Corynebacteria

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Corynebacterium diphtheriae

Can cause non-healing ulcer of the skin - cutaneous diphtheria

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Moist skin

Armpits, nostrils

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Moist skin has a high number of

Corynebacteria and staphylococci

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Most frequently isolated bacteria on skin

Staphylococcus epidermidis

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Staphylococcus aureus

Pathogen that causes boils, abscesses, wound infections

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Sebaceous skin has a high number of

Propionibacteria

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Propionibacteria

Anaerobic Actinobacteria that produce propionic acid as an end product of fermentation

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Propionibacterium acnes

Lives in hair follicles, and eats sebum - oil secreted by skin
Overgrowth can trigger inflammation - inflammatory acne

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Antimicrobial enzymes in saliva

Lysozyme and lactoperoxidase

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Lactoperoxidase

Catalyzes production of superoxide radicals O2 - oxidative damage to invading microbes

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What kinds of microbes does the mouth have?

Aerobic and anaerobic

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Neisseria mucosa

Aerobic
Lives on mucous membranes like the tongue

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Streptococcus mutans

Aerotolerant anaerobe

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Streptococcus mutans produces

A sticky dextran slime layer that lets it stick to surfaces - forms biofilms in crevices around the motor

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Streptococcus mutans produces what end-product

Lactic acid as an end-product of fermentation

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Streptococcus mutans degrades

Tooth enamel - dental carries

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Streptococcus mutans leads to

Inflammation along the gum line - gingivitis

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Stomach environment for microbes

Low pH and proteolytic enzymes make the stomach inhospitable to most microbes

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Helicobacter pylori

Colonizes surface of membrane, protected from stomach acid by mucous

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Helicobacter pylori

Exotoxin - kills cells in the membrane
Endotoxin - triggers inflammation

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What is the cause of stomach ulcers?

Helicobacter pylori

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What is helicobacter pylori treated with?

Antibiotics - tetracycline

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Small intestine environment

Area of rapidly changing pH
As pH becomes more neutral, bacterial numbers increase

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Enterococcus

Genus of gram positive lactic acid bacteria
Opportunistic pathogen

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What is the cause of nosocomial infections?

Enterococcus

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Enterococcus mechanism

Develop antibiotic resistance readily
Spread resistance genes on to other gram positive bacteria - horizontal gene transfer

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Large intestine environment

pH is neutral, environment anoxic
Enormous number of microbes ~ 10^11 cells/g of feces
Mostly anaerobes and facultative aerobes

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E. coli

Most cultured bacterium from feces - indicator of fecale contamination

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E. coli strain is

Non-pathogenic
May stimulate the immune system
Produce vitamin K

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What makes up less than 1% of bacteria in the large intestine?

E. coli

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What reveals E. coli is less than 1% of the large intestine?

16S rRNA

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Largest group of bacteria are strict anaerobes are from the genera

Bacteroides and Clostridium

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What roles does Bacteroides and Clostridium play?

Role in digestion

48

High number of methanogens play

A role in obesity

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Germ free mice vs. normal mice body fat

40% less body fat

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Innoculated germ free mice with microbes from healthy mouse intestines led to

Mice quickly gained weight

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Microbiomes of normal weight mice vs. genetically obese mice

Genetically obese mice had fewer Bacteroidetes, more Firmicutes and way more methanogens

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What do methanogens use to promote bacterial fermentation?

H2

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What does bacterial fermentation do for the host?

Make nutrients available

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Antibiotic associated colitis

Clostridium difficile grow
Inflammation of the colon

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Treatment of antibiotic associated colitis

Further antibiotics
Probiotics
"Transpoosition"

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Upper respiratory tract environment

Home to a variety of bacteria including staphylococci, streptococci, and corynebacteria

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What pathogen lives in normal microflora?

Staphylococcus aureus

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Lower respiratory tract environment

No resident microflora
Mucous, lysozyme, ciliated cells, secretory IgA, phagocytes

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Upper urinary tract environment

Normally free of microoganisms

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Urethra environment

Home to some gram-negative bacteria

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Normal microbiota in urinary tract

Can act as opportunistic pathogens

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E. coli in the urinary tract causes

Urinary tract infections

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Lactobacillus acidphilus in the vagina produces

Lactic acid from glycogen

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Lactic acid does what in the vagina

Lower pH and prevents growth of other microbes

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If normal microbiota in the vagina is disturbed

Yeast can overgrow and cause yeast infections