Microbiology Exam Two

Macronutrients

Required in relatively large quantities and play principle roles in cell structure and metabolism

• Carbon, hydrogen, nitrogen, phosphorus, oxygen

Micronutrients

Present in much smaller amounts, involved in enzyme function and maintenance of protein structure

• manganese, zinc, nickel, potassium, calcium, sodium

Heterotroph

Organism that must obtain its carbon in an organic form

Autotroph

Organism that uses inorganic CO2 as its carbon source

Phototroph

Photosynthesis

Chemotroph

Energy obtained from chemical compounds

Chemoheterotrophs

Derive both carbon and energy from organic compounds

• Processes molecules through cellular respiration or fermentation

Saprobes

Decomposers, free-living organisms

Characteristics of a psychrophile

• 0 - 10° C (optimal)

• Grow well in refrigerators

• Rarely pathogenic

Characteristics of a psychrotroph

• 15 - 30° C (optimal)

• Refrigerator temperatures

• Grow slowly in the cold

• Staphylococcus aureus and Listeria monoctyogenes

Characteristics of a mesophile

• 30 - 40° C (optimal)

• Majority of medically significant microorganisms

Characteristics of a thermophile

• 45 - 60° C (optimal)

• Live in soil or water associated with volcanic activity, compost piles, and sunny habitats

Characteristics of an extreme thermophile

• 65 - 85° C

• Often bacteria and archaea

• Hot springs

• Give us insight to our microorganism ancestors  

Three categories of oxygen usage

• Microbes that use and detoxify oxygen

• Microbes that can detoxify but not use

• Microbes that can do neither

Toxic oxygen products

• Singlet oxygen - O

  • oxidizes membrane lipids

• Superoxide ion - O₂^-

  • highly reactive

• Hydrogen peroxide - H₂O₂

  • toxic to cells

• Hydroxyl radical - OH^-

  • highly reactive

Reactions that remove toxic oxygen products

Superoxide dismutase:

2O₂^- + 2H⁺ —→ H₂O₂ + O₂

Catalase:

2H₂O₂ —→ 2H₂O + O₂

Aerobes

Can use gaseous oxygen in their metabolism and possess enzymes needed to process toxic oxygen products

• many bacteria, bacillus and TB

Microaerophiles

Harmed by normal atmospheric concentrations of oxygen but require a small amount of it in metabolism

• live in water and soil

• H. pylori

Facultative anaerobes

Do not require oxygen but use it when present

• Gram (-) interstitial bacteria

• Staphylococci

Anaerobes

Lack the metabolic enzyme systems for using oxygen in respiration

• oral + intestinal bacteria

Aerotolerant anaerobes

Do not utilize oxygen but can grow in a limited amount in its presence

• lactobacilli & streptococci, clostridial bacteria

Osmophiles

Live in habitats with high solute concentration

Halophiles

Prefer high concentration of salt

• Obligate halophiles: grow optimally in 25% NaCl solutions

• Facultative halophiles: resistant to salt

Mutualism

Obligatory but mutually beneficial relationship 

• Gut bacteria

Commensalism

One organism benefits, other is unaffected

• Staph on the skin

Parasitism

One organism benefits, other is harmed

Symbiosis vs synergism

Symbiosis - two organisms living together in close partnership

Synergism - An association between 2+ organisms that benefits them but is not necessary for survival

Antagonism

An association between a free-living species that arises when members of a community compete

Biofilm definition

Mixed communities of bacteria and other microbes that are attached to a conditioned surface and each other

Formation of a biofilm (steps)

1. a pioneer colonizer attaches to a surface (becomes sessile)

2. colonizers secrete extracellular polycheric substance (EPS)

3. other microbes attach to those bacteria, polymeric sugar, or protein substances. 

4. attached cells are stimulated to release chemicals as the cell population grows

activate genes and share them, help with antibiotic resistance, make channels for the bottom bacteria, grow on implants especially. 

What is binary fission

Where one cell becomes two!

• parent cell enlarges and duplicates its chromosomes

• Pulls cell envelope to center of cell

• Cell wall forms complete central septum

• division

Four phases of bacterial growth

• Lag - cells need to adjust to the new environment, begin multiplying

• Log - lots of available nutrients, rapid growth

• Stationary - nutrients start to dwindle, equal amount of cells are dying and multiplying

• Death - buildup of waste and lack of nutrients cause the death of many cells, except for some dormant cells. 

Disinfection

Destruction of vegetative cells from surfaces

• alcohol sprayed on counter

Antisepsis

Chemicals applied to living tissues to kill microbes without harming human cells.

• iodine for surgery

Decontamination/sanitation

Removal of most microbes to a safe level

• in a cafeteria or large space

Sterilization

Complete destruction of all microbial life

• used in labs and on surgical tools 

Relative resistance of microbes

Gram (+) —> nonenvveloped viruses —> fungi —> endospores—> prions

Bactericide vs bacteristatic

Bactericide: agent that destroys all bacteria (except for those in endospore stage)

Bacteristatic: often antiseptic drugs - inhibits the growth of bacteria

Microbial control on critical medical devices

MUST be sterilized, comes in contact to sterile tissues

Microbial control on semicritical medical devices

Come into contact with mucosal membranes, so must receive high level disinfection, preferably sterilized

Microbial control on noncritical medical devices

Only touch intact skin, low level disinfection

Factors that influence the action of antimicrobial agents

• Conditions of the population

• Conditions of the environment

• Properties of the control mechanism/agent

Microbicidal effect of moist heat

Coagulation and denaturation of proteins

Microbicidal effect of dry heat

Dehydrates cell and denatures proteins

Uses of filtration in medical context

• Used to prepare liquids that cannot withstand heat such as serum, blood, vaccines, drugs, IV fluids, enzymes, media

• High-efficiency particulate air (HEPA) used in hospital rooms

Aqueous vs tinctures

Aqueous - chemicals dissolved in pure water as the solvent

Tinctures - chemicals dissolved in pure alcohol or water-alcohol mixtures

Therapeutic Index

amount of drug that is toxic ➗minimum therapeutic dose

Inhibition of cell wall synthesis

• Penicillins and cephalosporins have beta-lactam ring

• Inhibits cross-linking of peptidoglycan

• Bacitracin + vancomycin

Inhibition of nucleic acid structure

• Fluoroquinolones 

• inhibit DNA unwinding

• ciprofloxacin

Inhibition of protein synthesis

Interference with cytoplasmic membrane

Inhibition of folic acid synthesis