Summary Medical Microbiology

Chapter 6 Summary Medical Microbiology ● Essential nutrients fuel the growth of all microorganisms ● Microbial genomes evolve in response to nutrient availability ○ As a result, some disease-causing bacteria have developed requirements for growth factors supplied by their hosts ● Autotrophs use CO2 as a carbon source ● Microbes obtain energy through phototrophy, lithotrophy, or organotrophy ● Heterotrophs consume organic compounds made by autotrophs ○ the global carbon cycle is made possible by the interactions between heterotrophs and autotrophs ● Nitrogen fixers, nitrifiers, and denitrifiers contribute to the nitrogen cycle ● A pure culture contains only a single bacterial species that is usually genetically homogeneous ○ Pure culture is needed for detailed molecular and biochemical studies of that species ● Bacteria can be cultured on solid or liquid media ● Minimal defined media contain only those nutrients essential for growth ● Complex, or rich, media contain many nutrients ○ Other media exploit specific differences between organisms and can be defined as selective or differential ● Microorganisms in culture may be counted directly under a microscope, with or without staining, or by using a fluorescence-activated cell sorter ● Microorganisms can be counted indirectly, as in viable counts and measurement of optical density ● A viable bacterial organism is defined as a cell with the ability to replicate and form a colony on a solid-medium surface