Microbial Nutrition, Growth, and Control Methods 9,11,12

Nutrients

C, H, O, N, P, S

Essential nutrient

Substances must be provided to an organism.

Growth factor

Organic compound such as an amino acid, nitrogenous base, or vitamin that cannot be made by an organism.

Heterotroph

Organism that depends on organic C from other living organisms.

Autotroph

Organism that uses inorganic CO2 and is not dependent on other living things.

Oxygen

Major component of organic compounds and common component of inorganic salts; O2 makes up 20% of the atmosphere.

Nitrogen

Primary sources for heterotrophs are proteins, DNA, and RNA; main reservoir is N2 in the atmosphere.

Ammonia (NH3)

Only form of nitrogen that can be directly combined with C to synthesize amino acids and other compounds.

Hydrogen

Maintains pH, forms bonds, and serves as the source of free energy in redox reactions of respiration.

Phosphorus

Main inorganic source is phosphate (PO43-); key component of nucleic acids and found in ATP.

Sulfur

Essential component of some vitamins and amino acids; forms disulfide bonds that help determine the shape and stability of proteins.

Chemotroph

Organism that uses a chemical source (organic chemicals) for energy.

Phototroph

Organism that uses light as a source of energy.

Saprobe

Free living organism that decomposes detritus and digests food particles into smaller molecules.

Parasite

Derives nutrients from the cells or tissues of a living host and can cause damage to tissues or even death.

Ectoparasite

Parasite that lives on the body of the host.

Endoparasite

Parasite that lives inside the organism in organs and tissues.

Intracellular parasite

Parasite that lives within the cells.

Obligate parasite

Parasite that is required to live inside a living host.

Diffusion

Movement from an area of high concentration to an area of low concentration until equally distributed.

Osmosis

Diffusion of H2O through a selectively permeable membrane.

Isotonic

Condition where there is no change in cell volume.

Hypotonic

Condition where the cell will swell and burst (lysis).

Hypertonic

Condition where the cell will shrivel and shrink.

Facilitated diffusion

Protein carrier used and no energy required, movement down the concentration gradient.

Active transport

Protein carrier and energy required, movement against the concentration gradient.

Endocytosis

Substances are engulfed into a cell.

Phagocytosis

Engulf cells or particles.

Pinocytosis

Engulf liquids.

Exocytosis

Package and release of substances from a cell.

Psychrophiles

Cold 0"-5"; optimum 15C to 30C; growth range 0C to 20C.

Psychrotolerant

Room temperature 25; 'food spoilers'; optimum 15C to 30C; growth is slow in colder temps.

Mesophiles

Body temperature 37; 'medical'; optimum 20C to 40C; majority of medically significant organisms, most human pathogens have optima 30C and 40C; growth range 10C to 50C.

Thermophiles

Hot 55" Celsius; optimum at temps greater than 45C, vary in heat requirements, growth range 45C to 80C.

Extreme thermophiles

> 80 degrees; growth range 80C and 121C.

Aerobes

Use O2 to grow.

Obligate aerobes

Requires O2.

Facultative anaerobes

Live with or without oxygen; doesn't require O2.

Anaerobe

Grow without oxygen.

Obligate anaerobe

Dies if exposed to O2.

Aerotolerant anaerobe

Don't use O2, but can survive grow to a limited extent in its presence.

Capnophiles

High CO2; grow best at higher CO2 concentrations than is normally present in the atmosphere.

Osmophiles

Live in habitats with a high solute concentration.

Halophiles

Prefer to live in high salt concentrations of NaCl.

Obligate halophiles

Grow best in 25% NaCl but require at least 9% NaCl.

Facultative halophiles

Resistant to NaCl, don't normally reside in high salt environments.

Barophiles

High pressure; deep-sea microbes exist under hydrostatic pressures ranging from a few times to over 1,000 times the pressure of the atmosphere.

Symbiosis

Occurs when organisms live together; one or both organisms requires the relationship to survive.

Mutualism

All benefit; mutually beneficial relationship.

Commensalism

One benefits and one unaffected; commensal receives benefits, while the other is neither harmed nor benefited.

Parasitism

One benefits and one harmed; host organism is harmed as it provides the parasite with nutrients and a habitat.

Synergism

Community of microbes that are living together; between free-living organisms that benefits them but is not necessary for their survival.

Biofilms

Quorum sensing- release chemicals as population grows to monitor its size.

Antagonism

Competition in the community; between free-living organisms that arises when members of a community compete.

Growth

Takes place on 2 levels: cell increases in size and number of cells in the population increases.

Binary fission

Asexual division; parent cell enlarges, chromosomes are duplicated, cell envelope pulls together in the center to form a septum, cell divides into 2 daughter cells.

Generation time

Time for a complete fission cycle, increases population by a factor of 2.

Lag phase

Inoculated, plenty of nutrients, few cells; population appears not to be growing.

Exponential growth phase

Cell division; growth curve increases dramatically, will continue as long as cells have adequate nutrients and favorable environment.

Stationary growth phase

Cell division and cell death, losing nutrients; population enters survival mode.

Death phase

Cell death, no nutrients left; limiting factors intensify, cells begin to die at exponential rate.

Turbidometry

Clear nutrient solution becomes turbid as microbes grow in it.

Direct (total) cell count

Counting the number of cells in a sample microscopically.

Coulter counter

Electronically scans a culture as it passes through a tiny pipette.

Flow cytometer

Similar to Coulter counter, also measures cell size and differentiates between live and dead cells.

PCR

Allows scientists to quantify microbes that are present in environmental and tissue samples without isolating and culturing them.

Sterilization

Destruction of all microbes.

Disinfection

Destroys most microbes and safe for use, reducing contamination on inanimate surfaces, also removes toxins.

Antisepsis

Destroys most microbes, reducing contamination on living surfaces.

Cidal agents

To kill; includes bactericide, fungicide, virucide, sporicide, germicide, microbicide.

Static agents

To stand still, prevent multiplication; includes bacteriostatic, fungistatic, microbistatic.

Thermal death time (TDT)

Shortest length of time to kill all microbes at a specific temp.

Thermal death point (TDP)

Lowest temperature to kill all microbes in 10 minutes.

Ionizing radiation

Ejects electrons, causing ions to form; damages proteins and DNA.

Nonionizing radiation

UV rays excite atoms but does not ionize them; damages DNA (thymine dimers).

Chemical agents: Halogens

Mode of action- proteins; includes fluorine, bromine, chlorine, iodine.

Chemical agents: Phenols

Mode of Action: proteins and cell membranes; destroy vegetative bacteria, fungi, some viruses.

Chemical agents: Alcohols

Mode of Action depends in part upon concentration; effective at 70%.

Chemical agents: Peroxygens

Mode of Action: proteins; can be toxic by product of O2.

Chemical agents: Surfactants

Mode of Action: cell membranes; disinfectants mixed with cleaning agents.

Chemical agents: Heavy metals

Mode of Action: proteins; includes mercury (Hg) and silver (Ag).

Chemical agents: Aldehydes

Mode of action: proteins; kills endospores and all microbes.

Chemical agents: Gases

Mode of Action: proteins and nucleic acids; includes ethylene oxide (ETO).

Prophylaxis

Use of a drug to prevent imminent infection of a person at risk.

Antimicrobial chemotherapy

Use of drugs to control infection.

Antimicrobials

All-inclusive term for any antimicrobial drug, regardless of what type of microbe it targets.

Antibiotics

Substances produced by the natural metabolic processes of some microbes that can inhibit or destroy bacteria.

Narrow-spectrum antibiotics

Antimicrobials effective against a limited array of microbes.

Broad-spectrum antibiotics

Antimicrobials effective against a wide variety of microbes.

Drug resistance

Adaptive response in which microbes tolerate a drug that would ordinarily be inhibitory.

Nephrotoxic

Toxic to kidneys.

Ototoxic

Toxic to eyes.

Neurotoxic

Toxic to brain.

Hepatotoxic

Toxic to liver.

Hemotoxic

Toxic to blood.

Superinfection

Microbiota destroyed by antibiotic.

MIC

Minimum inhibitory concentration.

Therapeutic index (TI)

Lowest risk of side effects versus highest probability of killing pathogen.

TI Formula

TI = Toxic dose / Effective dose.

Kirby-Bauer Disk Diffusion Assay

Standardized method to test antimicrobial susceptibility.