Lesson 9: Principles of Bacterial Growth Flashcards
refers to increase in number of cells and not the size of cells.
bacterial/microbial growth
which the bacteria undergo asexual cell division to produce two daughter cells genetically identical to the parent cell
binary fusion
begins with DNA replication and segregation of nucleoids (distribution between the future daughter cells)
Cell division
composed mainly of __________ assembled in the middle of the cell
Z-ring
FtsZ polymers
recruits additional proteins that serve for septum formation and subsequent separation of the daughter cells
Z-ring
is the time required for a bacterium to give rise to two daughter cells under optimum conditions.
Generation Time
replicates and multiplies rapidly producing millions of cells within 24 hours.
bacterium
Microbial concentration can be measured in terms of?
(i) cell concentration
(ii) biomass concentration
the number of viable cells per unit volume of culture
cell concentration
dry weight of cells per unit volume of culture
biomass concentration
the number of bacteria at a given time can be estimated by performing a?
total count or viable count
denotes the total number of bacteria in the sample, irrespective of wether they are living or dead.
total count
this is done by counting the bacteria under the microscope using counting chamber or by comparing the growth with standard opacity tubes
total count
indicates the number of living or viable bacteria
viable count
series of sequential dilutions used to reduce a dense culture of cells to a more usable concentration
dilution method
number of colonies that grow after a suitable incubation time
plating method
represents the number of live cells in a bacterial population over a period of time
bacterial growth curve
the time between inoculation and and beginning of multiplication. in this phase, the inoculated bacteria become acclimatized to the environment, switch on various enzymes, and adjust to the environmental temperature and atmospheric conditions. There is increase in size bacteria but no appreciable increase in number of bacterial cells
lag phase
this phase is characterised by rapid exponential cell growth of bacteria at their maximum rate.
log phase
are small and uniformly stained
bacterial cells
are sensitive to adverse conditions, such antibiotics and other antimicrobial agents
log phase
in this phase, the bacterial growth almost stops completely due to depletion of essential nutrients, water oxygen, change in pH of the medium, etc. and accumulation of their own toxic metabolic wastes (exotoxins)
stationary phase
endospore start forming during this stage
stationary phase
in this phase, the bacterial population declines due to death of cells due (a) accumulation of toxic products and autolytic enzymes and (b) exhaustion of nutrients
decline phase
involution forms are common in this stage
decline phase
is a method utilize for industrial and research purpose that is achieved by using a special device for replenishing nutrients and removing bacterial population.
continuous culture
physical requirements for bacterial growth
temperature, pH, osmotic pressure
the minimum and maximum temperatures for bacterial growth
30°C
the lowest temperature at which a species will grow
minimum temperature
when a species grow best
optimum temperature
highest temperature at which a species can grow
maximum temperature
refers to the alkalinity or acidity of a solution
pH
Most bacteria grow best near ___________. Few grow _________ and help preserve some food by bacterial fermentation.
neutral pH (6.5 - 7.5)
acidic pH (below 4)
the pressure required to stop water/solution from diffusing through a barrier by osmosis.
osmotic pressure
require water for growth and are made up of 80-90% water
microorganisms
when solution outside the cell has higher concentration of solutes than inside the cell, water is diffused outside of cell and the cell shrinks
hypertonic environment
when solution outside the cell has lower concentration of solutes than inside the cell, water is diffused inside of cell and the cells swells.
hypotonic
when concentrations in two solutions are same, so cell will neither swells nor shrinks.
isotonic
chemical requirements for bacterial growth
carbon, nitrogen, sulphur, phosphorus, trace elements, oxygen, organic growth factors
important for all organic compounds that make up a living cells, consist half the dryweight of a typical bacterial cell
carbon
helps from the amino group in amino acids
nitrogen
used to synthesize sulfur-containing amino acids and vitamins
Sulphur
important in synthesis of ATP, nucleic acids, phospholipids of cell membranes
phosphorus
minerals that are minimally required by microbes, and are also essential in enzymatic reactions
trace elements
required by aerobic microorganisms.
oxygen
oxygen is toxic to anaerobic bacteria like?
clostridium tetanus
what are the toxic form of oxygen
i. singlet oxygen
ii. superoxide free radicals
iii. peroxide anion
iv. hydroxyl radical
extremely reactive
singlet oxygen
highly unstable, steals electron from neighboring molecules thereby increasing free radicals
superoxide free radicals
most reactive form of oxygen
hydroxyl radical
are essential organic compounds that cannot be synthesized by an organism thus must be obtained from the environment
organic growth factors
example of organic growth factors
vitamins
