What do you need to do this week?On completion of week 2 studies on this module, you should be able to:• Explain some basic concepts from microbiology• Discuss the growth of bacteria, including factors which influence bacterial growth• Recognise a range of methods for the identification of bacteria and know how suchmethods are used in the examination of suspects foods• Discuss microbial criteria, using appropriate examplesAn important part of your learning experience this week is that you complete thefollowing tasks.
Task 2 A – Checking your basic microbiology knowledgeTask 2 B – Moisture requirements of microorganismsTask 2 C – Isolation of bacteriaTask 2 D – Usefulness and limitations of microbial criteriaSome basic concepts in MicrobiologyBacteria are single-celled organisms, or organisms consisting of cells that show littleor no differentiation, found in soil, air, water, on people, animals & food (Harriganand Park, 1991:1; Sprenger, 1998: 19). Bacteria are measured in micrometers (µm).Bacteria may be beneficial in the case of fermented foods such as cheese, wine,sauerkraut and a host of other products. However, two types of bacteria create majorproblems within the food industry (Sprenger, 1998: 8)Spoilage bacteria – responsible for the decomposition of foodPathogenic bacteria – responsible for causing illness such as dysentery,typhoid and food poisoning.Bacteria make up one of the subgroups of Microorganisms. It is important that youare able to distinguish between these subgroups as illustrated in the following Table:Contains representatives that areSubgroup Cell type Photosynthetic Motile MacroscopicBacteria Prokaryotic Yes Yes NoAlgae Eukaryotic All Are Yes YesFungi * Eukaryotic No No YesProtozoa Eukaryotic No Yes NoViruses Acellular No No No
The reproductive cell (spores) of some fungi are motile(source: Ingraham and Ingraham, 1995: 6)The terms bacteria and prokaryotes (procaryotes – modern American spelling) aresynonymous. The cell type “prokaryotes” means “before a nucleus” i.e. they lackinternal membrane bound structures. Ingraham and Ingraham (995: 269-270)distinguish ancient bacteria (archaebacteria) from true bacteria (eubacteria) basedon a different chemical compositionLike plants and animals, algae, fungi and protozoa, are eukaryotes (or eukaryotes –the modern American spelling), meaning “true nucleus”. They have a membranebound nucleus and other membrane-defined internal structures called organelles, ortiny organs.Viruses, are acellular (not a cell). A virus is a small packet of nucleic acid, thechemical form of genetic information, wrapped in a coat, usually made of protein.Although, not microorganisms, helminths, also have significance within the context offood safety.
The post Food Safety Management, Week 2: Bacteriology and Microbial Criteria
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