Intro to the Microbial World

Question 1

major cellular targets of antibiotics

Answer 1

• peptidoglycan synthesis
• RNA polymerase
• Cell mb
• Ribosome inhibitors

Question 2

how many bacterial species are in our microbiota

Answer 2

• thousands (about 1,000 - 10,000)

- there are also archaea present

Question 3

There are ____ times more bacterial cells than human cells in a person

Answer 3

10x

Question 4

The microbiota participates in…

Answer 4

• organ development
• digestion of food
• synthesis of vitamins

Question 5

changing perspectives on bacteria and human health

Answer 5

1) bacteria = most importantly agents of disease
2) most bacteria = harmless with only a few highly adapted which cause disease
3) hosts possess enormous, highly complex bacterial communities that are essential for health
4) (Now) the bacteria and the host have coevolved and continue to do so- the integration of their evolutionary histories makes them effectively inseparable

Question 6

Ways to test characteristics of bacteria

Answer 6

• measure their metabolism of sugars and other compounds - what is their prefered growth medium?
• test resistance to anti-microbials
• gram +/-
• identify the sugars used during, and the organic products of, fermentation
• determine if peroxidases or superoxide dismutatases are present: if so the bacterium can likely perform oxidative metabolism
• identify genes specific to a given pathogen

Question 7

how to identify bacteria by genes specific for a given pathogen

Answer 7

• analyze DNA from an infection site to determine whether pathogen-specific DNA is present
• must know genes unique to different pathogens
• can use PCR

Question 8

ways that diagnostic tests of bacteria can be contaminated

Answer 8

• avoid contamination from organisms present at the collection site
• beware of downstream contamination (blood banks)
• be suspicious of blood drawn from indwelling central venous catheters
• be knowledgeable about the real local pathogens- be suspicious of infections by organisms not known to be in the environment
• be meticulous about your own sanitation and stay home when sick

Question 9

timeline of infection by bacteria

Answer 9

1) exposure to pathogens
2) adherence to skin or mucosa
3) invasion through epithelium
4) colonization and growth production of virulence factors
5) toxicity and spread
6) disease
- neither adherence nor invasion have to occur
- colonization, growth, and spread all lead to more ppl being exposed to the pathogen and the cycle restarting for others

Question 10

how can a bacterium cause disease without invading or adhering

Answer 10

• alter gut microbiota
• produce a toxin
• collateral damage of the innate immune system
• bacteria can cause clogs in vessels, especially capillaries

Question 11

barriers to entry and adherence in the body

Answer 11

• lysozyme in tears and other secretions
• normal flora in whole GI tract
• skin- physical barrier, fatty acids, and normal flora
• low pH of stomach
• rapid pH change into small intestine
• removal of particles by rapid passage of air over cilia in nasopharynx (bacteria must adhere against gradient of air)
• mucus, cilia lining trachea
• blood proteins
• flushing of urinary tract

Question 12

direct consequences of adherence are …

Answer 12

• activation of the immune system
• uptake into a specialized double mb intracellular compartment
• cytoskeletal rearrangement, formation of a specialized lesion and entry into the host cell
• cytoskeletal rearrangement, formation of a specialized lesion, and some degree of entry into the host cell

Question 13

pathogens have preferred _____

Answer 13

niches

Question 14

what happens when a commensal bacterium enters a location in the body that it doesn’t normally occupy

Answer 14

-can become pathogenic or die because it has left its niche