Microbial Nutrition and Growth Overview

Essential nutrient

must be provided to an organism

Macronutrients

large quantities, role in cell structure and metabolism: Carbon, hydrogen, and oxygen

Micronutrients

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

Examples of micronutrients

manganese, zinc, nickel

Heterotroph

must obtain its carbon in an organic form

Autotroph

uses inorganic CO2 as its carbon source: Converts CO2 into organic compounds

Phototroph

photosynthesizes

Chemotroph

gets its energy from chemical compounds

Photoautotrophs

Photosynthetic; Produce organic molecules using CO2 that can be used by themselves and by heterotrophs

Chemoautotrophs

Chemoorganic autotrophs: use organic compounds for energy and inorganic compounds as a carbon source

Chemolithoautotrophs

rely totally on inorganic minerals and require neither sunlight nor organic nutrients

Chemoheterotrophs

Derive both carbon and energy from organic compounds

Saprobes

Eat dead things and recycle; feed on organic detritus from dead organisms

Parasites

Derive nutrients from the cells or tissues of a living host - from viruses to helminths

Pathogens

cause damage to tissues or even death

Ectoparasites

live on the body

Endoparasites

live in the organs and tissues

Intracellular parasites

live within cells

Obligate parasites

unable to grow outside of a living host

Common nutrients

Carbon, Oxygen, Nitrogen, Hydrogen

Essential Nutrients 2

In the table column 1 row 1, (N2) should read as N sub 2 within parenthesis; (NO3-, NO2-, or NH3) as N O sub 3 raised to the minus power comma N O sub 2 raised to the minus power, N H sub 3 within parenthesis; N 2 N sub 2; NH3 as N H sub 3

Essential Nutrients 3

In the table column 2 row 1, (P O43-) should read as P O sub 4 raised to the 3 minus power within parenthesis; (H3PO4) as H sub 3 P O sub 4 within parenthesis; and NAD+ as N A D raised to the plus power. In the table column 2 row 2, (S O42-) should read as S O sub 4 raised to the 2 minus power within parenthesis; (H2S) as H sub 2 S and B1 as B sub 1.

Potassium (K)

essential to protein synthesis and membrane function

Sodium (Na)

important for certain types of cell transport

Calcium (Ca)

stabilizer of cell wall and endospores of bacteria

Magnesium (Mg)

component of chlorophyll and a stabilizer of membranes and ribosomes

Iron (Fe)

important component of the cytochrome proteins of cell respiration

Zinc (Zn)

essential regulatory element for eukaryotic genetics

Diffusion

down their concentration gradient, no work, no energy required

Osmosis

the diffusion of water across a selectively permeable membrane

Tonicity

ability of a solution to cause a cell to gain or lose water

Isotonic solution

no net water movement across the plasma membrane

Hypertonic solution

solute concentration is greater than that inside the cell, cell loses water

Hypotonic solution

solute concentration is less than that inside the cell, cell gains water

Transport proteins

Channel proteins like a straw

Facilitated Diffusion

Passive Transport Aided by Proteins

Active transport

requires energy against their concentration gradients

Sodium-potassium pump

a type of active transport that requires energy

Bulk transport

across the plasma membrane for large molecules using vesicles

Endocytosis

reversal of exocytosis, includes pinocytosis and phagocytosis

Obligate aerobe

cannot grow without oxygen, examples include most fungi, protozoa, and many bacteria like Bacillus species and Mycobacterium tuberculosis

Microaerophiles

require a small amount of oxygen in metabolism, harmed by normal atmospheric concentrations of oxygen (~21%), examples include Helicobacteri pylori and Borrelia burgdorferi

Facultative anaerobes

do not require oxygen for metabolism but use it when it is present, examples include many gram-negative intestinal bacteria and staphylococci

Anaerobes

lack the metabolic enzyme systems for using oxygen in respiration, obligate anaerobes lack the enzymes for processing toxic oxygen and die in presence of oxygen, examples include many oral bacteria and intestinal bacteria.

Aerotolerant anaerobes

Do not utilize oxygen but can survive and grow to a limited extent in its presence.

Capnophiles

Organisms that grow best at a higher CO2 tension than is normally present in the atmosphere.

Cardinal Temperatures

Important temperatures by species: Minimum temperature is the lowest temperature that permits growth and metabolism; Maximum temperature is the highest temperature at which growth and metabolism can proceed before proteins are denatured; Optimum temperature is between the minimum and the maximum that promotes the fastest rate of growth and metabolism.

Psychrophiles

Have an optimum temperature below 15°C, capable of growth at 0°C, and cannot grow above 20°C.

Psychrotrophs

Grow slowly in the cold but have an optimum temperature between 15°C and 30°C.

Mesophiles

Grow at intermediate temperatures between 20°C and 40°C, and are the majority of medically significant microorganisms.

Thermoduric Microbes

Can survive short exposure to high temperatures but are normally mesophiles.

Thermophiles

Grow optimally at temperatures greater than 45°C, with a range of growth from 45°C to 80°C.

Neutrophiles

Organisms that thrive in a neutral pH environment.

Acidophiles

Organisms that thrive in acidic environments.

Minimum temperature

The lowest temperature that permits growth and metabolism.

Maximum temperature

The highest temperature at which growth and metabolism can proceed before proteins are denatured.

Optimum temperature

The temperature range between the minimum and maximum that promotes the fastest rate of growth and metabolism.

Natural habitats of psychrophilic bacteria

Lakes, rivers, snowfields, polar ice, and the deep ocean.

Storage at refrigerator temperature

Causes psychrophiles to grow rather than inhibiting them.

Human pathogens optimal temperatures

Have optimal temperatures between 30°C and 40°C.

Common contaminants of heated foods

Thermoduric microbes such as Bacillus and Clostridium.

Extreme thermophiles

Grow between 80°C and 121°C.

H+ and OH- interference

Interfere with H bonding in organisms sensitive to changes in acidity.

Staphylococcus aureus

A psychrotroph that can grow at refrigerator temperatures and cause food-borne illness.

Listeria monocytogenes

A psychrotroph that can grow at refrigerator temperatures and cause food-borne illness.

Alkalophiles

Organisms that thrive in alkaline environments, such as soils and water.

Vibrio cholerae

A bacterium that causes cholera, typically found in water.

Water

Most cells die in absence of water; endospores and cysts cease most metabolic activity.

Osmotic pressure

Restricts organisms to certain environments; affects the survival of obligate and facultative halophiles.

Hydrostatic pressure

Water exerts pressure in proportion to its depth, affecting organisms living under extreme conditions.

Barophiles

Organisms that live under extreme atmospheric pressure, such as deep sea bacteria and Archaea.

Xenophyophores

Giant unicellular Eukaryotes roughly the size of a basketball.

Symbiosis

A close partnership where two organisms live together.

Mutualism

An obligatory, mutually beneficial relationship between two organisms (+/+).

Commensalism

A relationship where one organism benefits while the other is neither harmed nor benefited (+/0).

Parasitism

A relationship where one organism provides nutrients and habitat to a parasitic microbe, causing harm to the host (+/-).

Antagonism

A competitive relationship where organisms compete for space and food.

Antibiosis

The production of inhibitory compounds (antibiotics) by one organism to inhibit another.

Synergism

A relationship that benefits both organisms but is not necessary for survival; they cooperate to produce a result that neither could do alone.

Biofilms

Mixed communities of bacteria and other microbes attached to a surface and each other.

Steps in Biofilm Formation

A pioneer colonizer initially attaches to a surface, allowing other microbes to attach and form complex communities.

Quorum sensing

A process where bacteria in biofilms monitor the size of their population by activating different genes.

Generation Time

The time required for a bacterial cell to grow and divide.

Heterotrophs

Organisms that obtain their food from organic substances.

Autotrophs

Organisms that produce their own food from inorganic substances.