Microbiology Exam 2 Material

Phototroph

uses light as its energy source.

Chemotroph

uses chemicals as its energy

source.

Autotroph

uses carbon dioxide (CO₂) as its

carbon source.

Heterotroph

uses organic compounds as its

carbon source

Most medically important microbe?

chemoheterotrophs

Enzymes

Biologic catalysts that speed chemical reactions; are highly specific to substrate

T or F: Enzymes are consumed during reaction

F

Substrate

reactant of an enzyme-catalyzed reaction

why do antimicrobials work?

bacterial enzymes differ from human enzymes

Enzyme Inhibitors

educe or stop enzyme activity

Catabolism

larger molecules → smaller

molecules; energy is released. "Degradative"

Anabolism

smaller molecules → larger

molecules; energy is required. "Biosynthetic"

Does building molecules require energy?

Yes

What does ATP stand for?

Adenosine triphosphate

What is ATP

major energy-

carrying molecule in cells

T o F: ATP transfers energy from catabolic reactions to

energy-requiring cellular work.

True!

ADP

From ATP to release usable energy

Biochemical Pathways

Sequence that each step is controlled by specific enzyme

Steps of Aerobic Reperation

1. Glycolysis

2. Krebs Cycle

3. Electron Transport Chain

Glycolysis

breaks glucose down through a stepwise enzyme pathway; generates pyruvate and a small amount of ATP.

Does glycolysis occur with oxygen?

NO! Occurs without

Krebs Cycle

produces the electron

carriers NADH and FADH₂,

which feed the ETC

ETC

transfers electrons through

oxidation-reduction reactions

What is the final electron acceptor in aerobic resperation?

Oxygen

What produces mosts of the ATP in Aerobic Repiration?

Oxidative phosphorylation

Fermentation

begins with glycolysis; yields very little ATP, about 2 ATP per glucose; does not involve oxygen; less efficient to Aerobic Respiration

Oxidation

loss of electrons; Oil Rig

Reduction

gain of electrons.

What occurs as a pair?

Oxidation and Reduction

Electron donor

reducing agent

Electron acceptor

oxidizing agent

Genome

complete collection of genes.

Gene

Segment of chromosome/DNA; direct cell functions

Phenotype

observable traits produced from the

genotype

Mutation

transmissible change in DNA; can be harmful, lethal or silent!

What can arise from mutation in a nursing/clinical standpoint?

Antibiotic Resistance

Plasmid

small extrachromosomal DNA molecule that

can carry useful genes; some carry antimicrobial/virus resistance; acquiring plasmid means acquiring new genes

Lysogenic conversion:

viral genes become part of the bacterial cell's biology

Transduction

a bacteriophage carries bacterial DNA

between bacteria.

Transformation

uptake of naked DNA from the environment; no phage or cell contact is required; is probably not

widespread in nature.

Competence

bacterium's ability to take up naked

DNA; competent bacteria can incorporate acquired DNA

Conjugation

direct cell-to-cell transfer, usually of plasmid DNA, through a mating bridge; attaches via sex pilus

Lysogenic conversion

phage DNA

integrates into bacterial

chromosome; viral genes create new

bacterial traits

Transduction

a phage carries

bacterial DNA from one bacterium to

another

Resistance factors

transfer multiple

antimicrobial-resistance genes at once.

Generation time

Time required for one

bacterial cell to divide into two.

Enriched medium

Contains extra

nutrients that support fastidious organisms.

Selective medium

Suppresses some

microbes while allowing others to grow.

Differential medium

Shows visible

differences between organisms that grow.

Inoculation

Placing a specimen or

microorganism onto or into culture media.

Incubation

Maintaining a culture under

controlled conditions so organisms can

grow.

Sterilization

destroys or eliminates all

forms of microbial life, including highly

resistant bacterial spores.

Disinfection

Reduces or destroys

pathogens on inanimate objects; spores

may survive.; on objects

Antisepsis

Use of antimicrobial

chemicals on living tissue

Aseptic technique

Practices used to

prevent contamination of specimens,

equipment, or sterile sites.

Bactericidal

Kills bacteria.

Bacteriostatic

Stops bacterial growth

and reproduction without necessarily killing

the cells

T o F: Most medically important microbes

grow best near neutral pH; the

textbook emphasizes about pH 7.0-

7.4

True

Thermophiles

Organisms growing best at high tempature

Mesophiles

Organisms growing best at moderate temperatures like 37 degrees C

Psychrophiles

Organisms preferring cold conditions, growing well at 4 degrees C

Hypertonic outside

water

leaves the cell. In

bacteria, the membrane

and cytoplasm pull away

from the cell wall; this is

plasmolysis

Hypotonic outside

water

enters the cell. The rigid

bacterial wall usually

prevents bursting

Isotonic

solute

concentration is

balanced and there is no

major net water shift.

Halophilic

organisms prefer salty

environments

Haloduric organisms

Can tolerate salt, but do not require it. EX Staphylococcus

Obligate aerobes

require oxygen and

grow well in an atmosphere similar to room air;

Microaerophiles

require less oxygen,

about 5% in the textbook example

Obligate anaerobes

harmed or

killed by oxygen

Capnophiles

grow best with

increased carbon dioxide,

commonly about 5-10%

How does bacteria reproduce?

Binary Fission

Generation time

time required for one

cell to become two; ex, Escherichia coli can divide in about 20 minutes

T o F: A culture can only be solid

False: culture can be liquid and solid

Enriched media

provide extra

nutrients for fastidious organisms.

Chocolate agar is a classic example

Selective media

inhibit some organisms while permitting others to grow

Differential media

reveal visible

differences among organisms that

grow.

Agar

has to replicate what it needs in its natural environment

Thioglycollate (THIO) broth

contains an oxygen

gradient: most oxygen near the top, least near

the bottom.

Oligate Areobes in Thioglycollate (THIO) broth

grow toward the oxygen-rich

top

Microaerophiles in Thioglycollate (THIO) broth

grow below the surface where oxygen is reduced.

Obligate anaerobes in Thioglycollate (THIO) broth

Grow where oxygen is

absent or extremely low.

Inoculation

placing part of a

clinical specimen onto or into culture media

spectrophotometer

estimates growth by measuring turbidity

viable plate

count measures living

organisms capable of forming colonies

Obligate intracellular pathogens

viruses and the bacterial

groups rickettsias and chlamydias; Modern diagnosis often relies on

nucleic-acid or antigen testing rather

than growing these organisms in

routine clinical culture

Fungi Culture

Medium and process differs COMPLETELY from bacteria

Microbicidal, germicidal, or biocidal

agents

Kill Microbe

Bactericidal agent

Kill bacteria but do not always kill bacterial endospores

Sporicidal agent

kill bacterial

endospores

Fungicidal agents

kill fungi

viricidal agents

inactivate or destroy viruses

Microbistatic and bacteriostatic

agents

inhibit growth and

reproduction rather than directly

killing.

autoclave

sterilizes with saturated steam under pressure

Desiccation

drying out/prevents

growth while organisms

may remain viable

Filtration

Physically removes microbes

Antimicrobial agent

a drug used to treat

an infectious disease by inhibiting or killing

pathogens in vivo.

Antibiotic

a substance produced by a

microorganism that kills or inhibits other

microorganisms.

Bacteriostatic

inhibits bacterial growth.

Bactericidal

kills bacteria.

Semisynthetic antibiotic

a naturally

derived antibiotic that has been

chemically modified