Ch 6 Microbial Growth Flashcards
what are psychrophiles
cold-loving microbes, grow at coldest temps, can grow below freezing (below 0C)optimum=12-15 C
what are mesophiles
moderate-temperature loving, optimum=37C
what are psychrotrophs
cant grow below 0C unlike psychrophiles, optimum=
22C
these 2 bacterial groups cannot cause infection bc they only survive at temperatures below body temp
psychophiles and psychrotrophs
all bacteria that cause infections are in this temp based group
mesophiles
this group of microbes is common in low temp food spoilage bc grows well in refrigerator temp
psychrotrophs
what are thermophiles
capable of growth at high temps, (opt 62C), seen in hot springs
what are hyperthermophiles
archaea opt- 80+C, seen in deep sea events that are under pressure or hot springs
importance of heating and cooling in food preservation
heat to a certain point to kill most microbes, cool to prevent more growth, in between is “danger zone”(15-52C)
why small containers of food are better than large for refridgeration
temp drops faster, goes thro danger zone quicker
optimum pH range for most bacteria
6.5-7.5
difference between autotrophs and heterotrophs in terms of C
autotrophs get CO2 from atmosphere
heterotrophs from other organisms
why bacteria need Carbon
C is structural backbone of living matter, needed for organic compounds that make up cell
why microbes need Nitrogen
synthesis of protein (form the amino group of amino acids in proteins), DNA/RNA, ATP
why microbes need sulfur
synthesize amino acids (therefore important in protein synthesis), makes vitamins such as thiamine and biotin
why microbes need phosphorus
essentilal for phospholipids of cell membranes, ATP, and synthesis of nucleotides (sugar-phosphate backbone of DNA)
these 2 trace elements are needed as cofactors for enzyme functioning
zinc, molybdenum , copper, and iron
why O2 is toxic for many organisms
in first 2 billion years on earth v little molecular oxygen, O2 is a powerful oxidizer (strips e- from others) causing metabolic problems
what bacteria have evolved to produce to reduce toxic effects of O2
enzymes Catalase and superoxide dismutase
catalase v. superoxide dismutase
Catalase neutralizes H2O2 (2H2O2–> O2 +2H2O)
superoxide dismutase=
2O2- (superradical) + 2H+–>O2 + H2O2
converts superradical into molecular O2
what are obligate aerobes
require O2
what are facultative anaerobes
prefer O2 but can grow without it (switch to anaerobic resp) but efficiency decreases
what are obligate anaerobes
only use anaerobic respiration
how catalase and superoxide dismutase work in conjunction
SOD converts superradical O2- into O2 producing H2O2 as a byproduct
catalase neutralizes this H2O2
what are aerotolerant anaerobes
only anaerobic but continue even in presence of O2 (tolerate it, but don’t use it)
difference between culturing obligate anaerobes and aerotoleant anaerobes
obligate need special techniques so no O2 is present , aerotolerant dont bc they can tolerate the presence of O2
many aerotolerant bacteria produce
lactic acid via fermentation
what are micoaerophiles
aerobic, cant tolerate too much or too little O2 (grow in O2 concentrations lower than that of air
what makes up the slime portion (matrix in which bacteria reside) of biofilms
primarily polysaccharides and some DNA and proteins
why quorum sensing important
allows bacteria to coordinate their activity and group together into communities
they also share nutrients, and are sheltered from environment, may also transfer genetic info between each other (conjugation)
biofilms are not just slime layers they are
biological systems
how a biofilm begins
a planktonic, free-swimming bacteria attaches to a surface
how biofilms avoid lack of nutrients at lower depths and buildup of toxic waste
form pillar-like structures with channels thro which water can carry incoming nutrients and outgoing wastes. (like a circulatory system)
how a biofilm extends
individual planktonic bacteria leave and move to new location
situations in which biofilms are importants
in rumen of ruminants to breakdown cellulose, also essential in sewage treatment systems
__% of human bacterial infections involve biofilms, they are (more or less) resistant to antibiotics
70%, more resistant
most nosocomial infections are caused by
biofilms on catheters
our latest approach to preventing biofilm formation is
incorporating antibiotics into surfaces in which biofilms might form. or finding a way to block quorum sensing.
difference between selective and differential media (medium= subs used to grow bacteria)
selective- supress growth of unwanted bacteria, encourage growth of desired
differential- allow distinguishing of types of bacteria
a pH sensitive indicator is an example of what kind of medium
differential
what are the 4 phases of the bacterial growth curve
Lag, Log, stationary, and death phase
bcterial growth curve: period of little- no cell division, intense activity preparing for pop growth (like replicating DNA)
1)Lag phase
bacterila growth curve: period of growth (logarithmic or exponential), generation time consistent
2) Log phase
bacterial growth curve: growth rate slows, number of deaths= number of new cells (equilibrium)
3) stationary phase
bacterial growth curve: number of deaths exceed the number of new cells, population decreases at logarithmic rate
4) death phase
how to use a serial dillution to count bacteria
take an innoculation dilute into inceasing dilutions (1:10, 1:100, 1:1000, etc.) until # of CFUs is reasonable to count
how to calculate # of cells after counting one of its serial dilutions
of cells x dillution factor
optimal pH range for molds and yeasts
5-6
complex media v. chemically defined media
chem defined: exact contents are known, good for growing bacteria w specific requirements
complex: unknown contents, made of nutrients from extracts from yeasts, meat etc. (ex: peptone (partially digested proteins, beef extract, etc.)
a basic microbiology lab would be what biosafety level
1
our lab (one that involves sterile technique) is which biosafety level
2
