Introduction to Microbiology

Question 1

microbiology

Answer 1

the study of microbes, organisms too small to be seen by the unaided eye

this has now been broadened to include larger parasites

Question 2

medical microbiology

Answer 2

a focus on those microbes that cause infections in people

Question 3

infectious diseases

Answer 3

the medical subspecialty focused on the illnesses caused by microbes

Question 4

microbiome

Answer 4

the microbes that make up our normal flora

outnumber our own cells 10:1

important for development of immune system, obesity, heart disease

provides defense againt infection

Question 5

eukaryotes vs. prokaryotes

Answer 5

eukaryotes have nuclei with nucelar membrane, internal membrane networks, introns, and organelles

prokaryotes have chromosome in cytoplasm, cell wall, no internal membrane networks, no introns

Question 6

bacterial morphology - shapes

Answer 6

cocci - round

bacilli - rods

coccbacilli - inbetween

spirochetes - corkscrew shape

Question 7

bacterial morphology - structural properties

Answer 7

individual cells

in pairs

chains of connected cells

clusters

Question 8

bacterial size

Answer 8

E. Coli - 2 microns to 0.5 microns

staphylococcus aureus - ~1 micron

treponema pallidum - spirochete, small diameter, length of 5-15 microns

in general, bacteria 1-2 microns

Question 9

bacterial cell envelope

Answer 9

surrounds the cytosol

protection from environmental threats

housing for factors important in many cellular functions

consists of at least two parts - cytoplasmic membrane and cell wall

Question 10

cytoplasmic membrane

Answer 10

permeability barrier

electron transport

export of membrane and secreted proteins

biosynthesis of cell wall components

partition of the newly replicated chromosome into daughter cells during cell division

Question 11

cell wall

Answer 11

gives shape

protects the cell against osmotic lysis

all medically important bacteria except mycoplasmas and chlamydia have cell walls

Question 12

peptidoglycan

Answer 12

a unique component of the bacterial cell wall, also known as murein

antibiotic target

made up of acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Question 13

peptidoglycan structure

Answer 13

NAG and NAM

peptide of alternating L- and D-amino acids

the third amino acid of some peptides are crosslinked to the terminal amino acids of other peptides

penicillin-binding proteins facillitate synthesis

Question 14

penicillin binding proteins (PBPs)

Answer 14

responsible for the proper cross-linking of chains of peptidoglycans and are therefore good targets for antibiotics, such as penicillins

Question 15

peptidoglycan synthesis in the precense of penicillin

Answer 15

blocks the PBPs and prevents cross-linking that form the sheets

Question 16

mechanisms of bacterial resistance to penicillins

Answer 16

beta-lactamase production

alteration of PBPs

prevention of access

Question 17

peptidoglycan synthesis in the presence of vancomycin

Answer 17

prevents cross-linking through methods other than blocking PBP function

Question 18

vancomycin-resistant enterococci

Answer 18

changed the D-alanine-D-alanine bond to a D-alanine-D-lactate bond, which prevents vancomycin binding

Question 19

lysozyme

Answer 19

enzyme that claves specific bonds in peptidoglycan, yielding NAGA-NAMA disaccharides

found in saliva, mucous secretions, tears, neutrophils

Question 20

gram-positive bacteria

Answer 20

bacteria with thick cell walls, which contain teichoic acids

Question 21

gram-negative bacteria

Answer 21

bacteria with thin cell walls

contain two lipid bilayer membranes, the cytoplasmic and oute rmembranes

the region between the two membranes is the periplasm, which is filled with elaborate glucan sturctures that help regulate the osmolarity of the cell

Question 22

Describe the staining process for gram positive versus negative bacteria.

Answer 22

application of crystal violet, which is taken up by all cells

iodine added next, then alcohol wash

gram positive bacteria with thick walls will retain the violet and iodine

gram negative bacteria will lose the violet color and can then be counter-stained with safranin

Question 23

Ziehl-Neelsen or Kinyoun staining

Answer 23

used for bacteria that have long-chain fatty acids

also called the acid-fast staining

ex. mycobacteria

Question 24

darkfield microscopy

Answer 24

light strikes speciment at an angle, only deflected light enters objective

used for bacteria that are so thin that they can’t be seen with light microscopy

Question 25

limitations of Gram-staining

Answer 25

mycobacteria needs acid-fast staining spirochetes need dark-field microscopy mycoplasma, chlamydia have no cell wall rickettsias and legionella don't stain well but the reason is unknown

Question 26

teichioic acids

Answer 26

long polymers of either glycerol phosphate or ribitol phosphate that also contain sugars and amino acids attached to either the cytoplasmic membrane or the cell wall adhesins exact structure varies from bacteria speciies to species

Question 27

Lipid A

Answer 27

a diglucosamine molecule containing substituted fatty acids lipid A is the component of LPS that is embedded in the outer membrane in addition, the toxic effects of LPS are due to lipid A

Question 28

lipopolysaccharide (LPS)

Answer 28

replaces phospholipids in gram-negative bacteria contains three parts - lipid A, core polysaccharides, and O antigen five to seven saturated fatty acid side-chains form tight barriers that prevents many molecules such as antibiotics from reaching the cell wall extremely toxic to humans, induces fever

Question 29

core polysaccharide

Answer 29

a region attached to lipid A conisting of 7-9 sugar residues (including some unusual ones such as ketodeoxyoctonate (KDO) and heptose)

Question 30

O antigen (or O-specific side chain)

Answer 30

a polysaccharide chain consisting of repeating units of 3-5 sugar residues O antigenic chain is not present in all Gram-negative organisms when present, it is antigenic and allows serotyping of many bacteria long O-side chains are protective against complement-mediated lysis and cause bacteria to be **serum resistant** bacteria lacking the long O-side chains cannot be targeted by antibodies but are susceptible to complement -mediated lysis and are **serum sensitive**

Question 31

endotoxin

Answer 31

another name for LPS, toxicity caused by lipid A at low concentrations it induces fever and stimulates B cells and macrophages, activates complement and the acute pohase response at high concentrations it causes septic shock, which is characterized by hypotension, criculatory collapse, disseminated intravascular coagulation, multiple organ failure, and death

Question 32

CD14 receptors

Answer 32

receptors on monocytes and macrophages that interact with LPS through **LPS-binding protein** activates a membrane protein called toll-like-receptor 4 (TLR-4)

Question 33

TLR-4

Answer 33

toll-like receptor-4 a membrane protein on monocytes and macrophages that triggers the production of cytokines such as iL-1beta and TNF-alpha