Module 2.2- Bacterial Growth and Nutrition Flashcards
microbial growth pertains to:
number of cells
groups of cells large enough to be seen without a microscope
colony
Bacteria increase in number by an asexual means of reproduction which is
binary fission
3 stages of binary fission
- increase cellular structure, components, and mass
- chromosomes are replicated and segregated
- a septum forms and divides progeny cells
refers to the time required for the bacterial cell to divide, thus doubling their population
generation time
generation time is mathematically expressed as
GT = t/n
(t =time for 1 generation)
(n =number of generation
graph that represents the number (expressed as logarithm) of viable cells in a bacterial population over a period of time
bacterial growth curve
4 distinct phases of growth when bacteria are cultivated in liquid medium in a closed system or batch culture
- lag phase
- log phase (exponential growth phase)
- stationary phase
- decline phase
bacterial phase of adaptation to their new environment, and undergoing a period of intense metabolic activity involving, though there is little or no cell division.
lag phase
phase where cell division proceeds at maximal rate and the bacterial population is in the state of balanced growth, i.e., the number of cells increase proportionally over the same period of time
log phase (exponential growth)
Bacterial population in this phase is preferred for laboratory testing, e.g., motility, staining
log phase (exponential growth)
the bacterial population is decreasing in a logarithmic rate.
Decline (or death) phase
growth curve becomes horizontal and at its greatest population density,
Stationary phase
Stationary phase is also known as
plateau phase
The bacterial population is in the state of balanced growth,
Log (or exponential) phase
cell division stops completely and the number of deaths exceed the number of new cells formed,
Decline (or death) phase
This is the period of equilibrium where the total number of viable microorganisms remains constant. This may result from a balance between cell division and cell death, or the population may simply cease to divide but remain metabolically active.
stationary phase
2 requirements for bacterial growth
nutrional and physical requirements
4 main nutritional requirements of bacteria
- major elements (C, H, O, N, S, P, K, Mg, Fe, Ca)
- trace elements (Mg, Co, Z, Cu, Mo)
- Carbon and energy
- Growth factors
Nutritional requirement that are supplied by inorganic ions, water molecules, small molecules, and macromolecules, and serve as either structural or functional role in the cells.
major elements
Nutritional requirement that is needed by certain cells in small amounts that is difficult to detect or measure, and are present as contaminants of water or other cell membrane components.
trace elements
nutritional requirements classified as organic compounds that are essential for growth that the organism is UNABLE TO SYNTHESIZE, and fulfill a specific role in biosynthesis
growth factors
nutritional requirement that is the structural backbone of living matter
carbon
Three categories of growth factors
- purines and pyrimidines
- amino acids
- vitamins
growth factors that are required for synthesis of nucleic acid.
purines and pyrimidines
growth factors that are used by some bacteria for synthesis of proteins, especially by certain pathogenic bacteria requiring specific types of growth factors for their isolation outside a host’s body.
amino acids
2 amino acids that Neisseria requires
cystine and cysteine
growth factors needed by some bacteria as coenzymes and
functional groups of some enzymes.
Vitamins
Bacteria that have special nutritional requirements, esp. growth factors are described as
fastidious
Four major physical requirements of a bacteria
- gaseous requirement
- Temperature
- pH
- Ionic strength/osmotic pressure.
gas that has the greatest impact on bacterial growth.
Oxygen
An organism able to grow in the
presence of atmospheric O2
aerobe
An organism that can grow in the absence of atmospheric O2
anaerobe
completely dependent on atmospheric O2 (20-21% concentration) for growth.
Obligate aerobe
does not tolerate O2 at all and die in its presence (> 0.5% concentration)
Obligate or strict anaerobe
is an aerobe but can grow in the
absence of O2.
Facultative anaerobe
an anaerobe but can grow in the
presence of O2..
Aerotolerant anaerobe
requires reduced O2 (2-10%) concentration.
Microaerophile
forms of oxygen free radicals
- Singlet oxygen
- Superoxide radical or superoxide anion
- Peroxide anion
- Hydroxyl radical
an extremely reactive molecule produced by both living and non-living processes.
Singlet oxygen
formed in small amounts during the normal respiration of organisms that use oxygen as a final electron acceptor, forming water.
Superoxide radical
forms when an oxygen molecule combines with another oxygen molecule.
Peroxide anion
formed in the cell cytoplasm by ionizing radiation.
Hydroxyl radical
examples of bacteria enzymes that allow them to detoxify harmful forms of oxygen and not be affected by its presence.
- Superoxide dismutase
- Catalase
- Peroxidase
converts the superoxide radical
into molecular oxygen (O2) and hydrogen peroxide (H2O2).
Superoxide dismutase
produced by some bacteria in response to the formation of toxic hydrogen peroxide (H2O2) during normal aerobic respiration. It converts H2O2 into water and oxygen.
Catalase
Another enzyme that breaks down hydrogen peroxide. However, it differs from catalase in that its reaction does not produce oxygen.
Peroxidase
a chemical that absorbs O2 gas and renders it unavailable to the bacteria where only he surface, which is directly exposed to atmospheric O2, will be oxic.
thioglycollate
Bacteria that grow best at a higher (3% to 10%) CO2 tension than is normally present in the atmosphere (0.1%)
capnophile or capneic
lowest temperature at which the species will grow.
Minimum temperature
the temperature at which the species grows best.
optimum temperature
the highest temperature at which growth is possible.
Maximum temperature
cold- loving microbes
Psychrophiles
Psychrophiles grow best at
0C–15C
Psychrophiles grow best at
0C–15C
moderate-temperature- loving microbes
Mesophiles
Mesophiles optimum temperature for growth fall into the range of
20C to 40C
Pathogenic bacteria fall under this category.
Mesophiles
Pathogenic bacteria fall under this category.
Mesophiles
the optimal temperature of pathogenic bacteria
37C
heat-loving microbes
Thermophiles
general range of growth of Thermophiles
45C - 80C
Most bacteria grow best in a narrow pH range near neutrality, between ___
6.5 and 7.5.
bacteria that grow best
at a pH range of 1.0 to 5.5.
Acidophiles
bacteria that grow in environments with a pH greater that 8.5.
Alkalinophiles
grow best at a pH between 6.0
to 8.0
Neutrophiles
require environment with high solute (e.g., salt or sugar)
concentration
Osmophile
requires a high salt (NaCl) concentration for growth.
Halophile
has the ability to withstand large changes in salt concentration.
Halotolerant
open systems in which microbial populations are maintained by continuing to supply fresh nutrients to the incubation vessel while simultaneously removing toxic
wastes and excess microorganisms.
continuous cultures
most common type of continuous
culture device used is
chemostat.
