Lecture 1: physical and chemical requirements of microbial growth Flashcards
microbial growth def
increase in bacterial numbers
what is the septum
the dividing wall that forms across the middle of a bacterial cell, effectively splitting it into two daughter cells during the process of cell division
what causes the shape and arrangement of bacterial cells
the plane of division that has occurred during binary fission
shapes and arrangements of bacterial cells
shapes = cocci and rod
arrangements = chains and clusters
what does division in one plane form
diplococcus
what does division in two planes form
streptococcus
what does division in many planes form
cluster
what cell size is advantageous
a smaller cell size as there is a larger surface to volume ratio
physical factors that influence microbial growth
- gaseous atmosphere
- temperature
- ph
- osmotic pressure
chemical factors that influence microbial growth
- water
- energy and electron source
- carbon
- micronutrients
- macronutrients
gaseous atmosphere
microbes vary in their need for and tolerance of oxygen
aerobes
require molecular oxygen (aerobic respiration)
–> electron transport chain, then final electron acceptor is oxygen
anaerobes
prefer the absence of oxygen (anaerobic respiration or fermentation)
–> anaerobic respiration uses electron transport chain, the final electron acceptor is exogenous
what happens during fermentation
- there is no electron transport chain (or generation of PMF)
- ATP is synthesised by substrate level phosporylation, electron acceptor is endogenous
capnophiles
require increased levels of carbon dioxide (around 5% which is more than what is in the environment naturally)
obligate aerobes
need oxygen
facultative anaerobe
prefer oxygen
aerotolerant anaerobe
tolerate oxygen
strict anaerobe
oxygen is toxic
microaerophile
2-10% oxygen
how can oxygen be toxic
- it can be converted by metabolic enzymes into highly reactive derivatives
- aerobes can tolerate it bc they convert the toxic substances using enzymes
- anaerobes do not possess these enzymes and so cannot tolerate oxygen
reactive oxygen species (ROS)
superoxide and hydrogen peroxide
5 different bacteria species and their temp preference (coldest to hottest)
psychrophiles
psychrotolerants
mesophiles
thermophiles
hyperthermophiles
different pH solutions
- isotonic
- hypertonic
- hypotonic
why dont bacterial cells burst
because they have a rigid wall
how is water impacted and what does it impact
Impacts osmotic pressure
And
is impacted by temperature
categories of organism based on their energy source
- phototrophs
- chemotrophs
phototrophs
derive energy from sunlight
chemotrophs
energy derived from oxidation of chemical compounds (organic or inorganic)
electron source may be from
reduced inorganic subastances = lithotrophs
reduced organic compounds = organotrophs
two terms used to characterise organisms according to the carbon sources which they utilise
- autotrophs
- heterotrophs
autotrophs
utilise only inorganic carbon in the form of carbon dioxide
heterotrophs
utilise organic carbon (proteins, carbs and lipids)
chemo organoheterotrophs
the combined terms for energy, electron and carbon source
macronutrients
Def: a type of food required in large amounts in the diet
eg: carbon, hydrogen, nitrogen, oxygen, phosphorus, sulphur
micronutrients
Def: a chemical element or substance required in trace amounts for the normal growth and development of living organisms
Eg: zinc, cobalt, molybdenum, copper, manganese
