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Bacterial growth

Bacterial growth. Objectives. To know the nutritional and environmental requirements for bacterial growth To know the media used for culturing in the laboratory To know the atmospheric factors influencing growth. Growth curve. A lag phase During which bacteria are preparing to divide

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Bacterial growth

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  1. Bacterial growth

  2. Objectives • To know the nutritional and environmental requirements for bacterial growth • To know the media used for culturing in the laboratory • To know the atmospheric factors influencing growth

  3. Growth curve • A lag phase During which bacteria are preparing to divide 2. A log (exponential) phase During which bacteria numbers increase 3. A stationary phase In which the nutrients are becoming limited and the numbers and the number of bacteria remain constant 4. Death phase When the number of nonviable bacterial cell exceeds the number of viable cells

  4. Environmental factors influencing growth • pH: (between 7-7.5) • Temperature: Bacteria according to their optimal temperature into • Pyschrophiles optimal growth at 100-200C • Mesophiles: optimal growth at 200-400 C • Thermophiles: grow at high temperature at 500-600 C • Gaseous composition of the atmosphere

  5. Environmental factors influencing growth • pH: (between 7-7.5) • Temperature: Bacteria according to their optimal temperature into • Pyschrophiles optimal growth at 100-200C • Mesophiles: optimal growth at 200-400 C • Thermophiles: grow at high temperature at 500-600 C • Gaseous composition of the atmosphere

  6. Types of growth media • Basal media The contents are simple and complete( not used in diagnostic laboratory) • Nutrient media (broth) Are more complex and made of extract of meat or soy beans • Enriched media (blood and chocolate) Contain added growth factors (blood, vitamins, yeast extract • Selective media (MacConkey) Inhibit the growth of some bacteria and allow others to grow • Differential media Allow the visualization of metabolic differences between bacteria • Transport media Holding medium deigned to preserve viability of bacteria in the specimen but not allow multiplication

  7. Gaseous composition of the atmosphere • Obligate aerobes Require oxygen for growth • Obligate anaerobes Cannot grow in the presence of oxygen • Facultative anaerobes Can grow either with or without oxygen • Capnophilic Grow better in the presence of carbon dioxide • Microaerophilic Require reduced level of oxygen to grow

  8. Microbial growth and nutrition All bacteria have three major nutritional needs for growth • A source of carbon (for making cellular constituents) • A source of Nitrogen (for making protein) • A source of energy (ATP) for carrying out cellular functions • Others like phosphate ( for nucleic acid synthesis), metals and ions (for enzymatic activity

  9. Clinical samples • Blood • Urine • Stool • Swabs • Sputum • Body fluids • CSF

  10. Cultural Characteristics In clinical terms, it is the shape, size, color, elevation and other characteristics of the colony formed on the culture plate Identification of Specimens 􀂉 Type of specimen 􀂉 Collection date and time 􀂉 Laboratory number 􀂉 Laboratory findings 􀂉 Tests requested 􀂉

  11. Culture Methods •To isolate bacteria in pure culture from clinical specimens •For identification of bacteria •To determine antibiotic susceptibility •To prepare antigens for serodiagnosis •To maintain stock cultures

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