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bacterial fungus

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Chemistry and Biochemistry

Bacteria (single celled, prokaryotic)  Only small number are pathogens  Asexually reproduction by binary fission / 2 identical daughter cells  Grow best at optimum conditions (human body) o Constant temperature o Neutral pH o Constant supply of food, H2O, O2 o Mechanism removing waste  Most bacteria are aerobic / obligated aerobes  Aerobic bacteria growing with absent oxygen / facultative anaerobes  Bacteria which find oxygen toxic / obligate anaerobes Sigmoid growth curve shows the number of bacteria plotted against time  Bacteria MUST grow in closed system and nutrient medium → BACTERIAL CULTURE o 1) Population grows slowly - LAG PHASE o 2) Rapid increase of population growth - LOG PHASE o 3) Reaches equilibrium when number remains constant - STATIONARY PHASE  Lag Phase → initial phase o Low number of reproducing organisms o Bacteria increase in size before division o This requires nutrients which need to be digested o Digestion requires enzymes, proteins → activation of genes → time consuming process  Log Phase → exponential phase; max growth rate; steep curve o Optimum conditions: no limiting factors, waste does not accumulate to a toxic level o Bacteria most susceptible due to production of new cells  Antibiotics inhibit cell wall formation  Antibiotics inhibit DNA replication  Antibiotics inhibit protein synthesis  Stationary Phase → reduced growth rate o New cell production balanced by death of cells o Limiting factors, declining nutrients, accumulating waste influence population size  Decline Phase → bacteria stop dividing o Death rate increases; numbers may fall to zero o Lack of nutrients, build up of toxic waste products  Aseptic conditions o Sterilise equipment, instruments, thus, to prevent contamination with the culture. o Use high temp and disinfectants Total cell count  Number of cells whether living or dead  Count cells with haemocytometer  Stop bacteria entering the flask with a stopper. Important as bacteria would have been caused reduced growth rate of yeast/killed yeast and competed for space/nutrients  Culture is shaken to achieve a uniform distribution of yeast cells/spread out yeast  Larger number is taken to avoid anomalies/produce an average Measurement of growth Generation time: time taken for a bacterial population to double  Rate of population o = increase in number of yeast cells/time o = number larger - number less/(time larger - time less)  Suppose the number of cells in one square are 6 8 9 5 7  The sum of the cells in 5 squares is 35
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