Study GuideMicrobiology–Microbial Cultivation and Growth1.Growth Requirements for MicroorganismsOne of the defining features of microorganisms is their ability togrow and multiply, forming largepopulations. Microbial growth occurs when cells increase in size and then divide. For this growth tohappen successfully, microorganisms need specificchemical and physical conditions.1.1Chemical Requirements for Microbial GrowthTo grow and survive, microorganisms must obtain a variety of chemical substances from theirenvironment.Water and Carbon•Wateris essential for all life processes.•Almost all organic compounds in microorganisms—such as proteins, carbohydrates, fats, andlipids—containcarbon.•About50% of the dry weight of a bacterial cell is carbon.Sources of carbon:•Organic carbonfrom environmental materials•Carbon dioxide (CO₂)from the atmosphereMicroorganisms that use CO₂as their carbon source include:•Chemoautotrophs–obtain energy from chemical reactions•Photoautotrophs–obtain energy from sunlight through photosynthesisNitrogen and Phosphorus•Nitrogenis required for making:Preview Mode
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