4py019 pharmacy notes - bacteria/ microbiology, Lecture notes of Pharmacy

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Bacterial growth: Growth- increase in the number of cells Bacterial reproduction can occur in several ways including: Binary fission: Occurring most in commonly encountered bacteria when cell enlarges & divides into 2 Budding: Small projections at the end of the cells which enlarge i.e. rhodopseudomonas acidophila Filamentous growth: Cells fragment into smaller units i.e. nocardia spp. Expospore formation: External spores formed at the hyphae tips i.e. streptomyces species Binary fission: Due to the lack of nuclei, mitosis/meiosis cannot occur so they undergo binary fission instead. The original single chromosome is duplicated and with 2 copies, the cell can elongate to 2 separate chromosomes. Between the 2 copies of chromosomes, a septum begins to form by pinching in gram +ve and growin in gram -ve. Once the septum finished forming and divides the one bacterium into 2 be3coming separate 2 daughter bacteria. Prokaryote cell division: Some proteins essential for division are filamentous temperature sensitive Fts which interact to form divisome. This occurs when FtsZ form a ring around the cell centre. There are ma ny Fts proteins attracted to the ring. Autolysins digest peptidoglycan that is already pre-existing and beginning at FtsZ ring The divisome synthesis’s new cytoplasmic membrane Batch culture bacterial populations growth: 4 phases involved in this i.e. in liquid medium 1)lag phase 2)log phase 3)stationary phase 4)death phase

Total cell count: A microscope is used to count all cells both live and dead on dried samples on a slide or liquid samples using a counting chamber i.e. haemocytometer However, this does not distinguish from live and dead, the small cells may be difficult to count, this is not suitable for low cell density samples and most cells must be immobilized Viable cell counts or plate counts: The measurement of living and reproducing population This can be performed by spread-player methods and pour-plate methods to obtain the appropriate colony number in which the counted sample should always be diluted However, the colony number can alter the length of incubation, there may be pipetting errors and also cell clumping Count plates versus microscopic count- reasons for anomalies may e due to microscopes counting both dead and living cells, different nutritional requirements or culture conditions Microbial mass: Turbidimetric method is useful during the exponential growth for measuring the mass of increased protein, DNA, dry weight or culture. Optical density measured using a spectrophometer. A standard curve must be produced in order to link absorb acne readings to direct counts 260nm DNA, 280nm protein, 600nm cultures Biofilms: May produce self defence, allowing cells to remain in a favourable niche and to live in close association, a typical way bacterial cells grow in nature Bacterial cells require certain nutrition such as carbon, nitrogen, phosphorus, sulphur, potassium, magnesium, sodium, calcium, iron Selective media contains inhibiting growth compounds of specific microorganisms bout differential media is an indicator used i.e. dye to distinguish between different metabolic and chemical reactions in organisms