Toxins are specific microbial products or secretions which at very low concentrations can act specifically on the cells and tissues of other organisms including humans to cause a local or systemic damage. Toxins which are found in both Gram-positive and Gram-negative bacteria help to increase the pathogenicity and virulence of a given pathogen once they […]
Bacterial pathogens that cause infections in humans have innate characteristic mechanisms with which they use to suppress the immune response of their host in their bid to establish a disease process. Initiation of an infectious process leads to the development of signs and symptoms in the human host, and these syndromes helps to announce the
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Bacteriology
Inoculum size is defined as the number of invading pathogenic microorganisms that is sufficient enough to initiate an infectious process (i.e. an infection) in a susceptible human host. Pathogens must reach or exceed a particular threshold before they will be able to produce clinical signs which are unique to a given disease process. Normally, the
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Bacteriology
Continuous fermentation is defined as the fermentation process in which sterile growth nutrients are added continuously to the fermentation vessel and an equal amount of converted nutrient solution (end-product) with microorganisms is simultaneously harvested in the process. It is also known as an open culture system – since it allows nutrients to be continuously added
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Industrial Microbiology
Fed-batch fermentation is defined as the liquid fermentation process in which growth nutrients are periodically added in the fermentation medium during fermentation. The process is akin to batch fermentation process except that small concentrations of nutrients are added at the beginning of the process, and there is a continuous addition of nutrients during the process
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Industrial Microbiology
Batch fermentation is defined as the liquid fermentation process in which the culture is inoculated into a sterile medium contained in a closed vessel. In batch fermentation process, there is no addition of nutrients once the fermentation process starts. This type of fermentation process can also be known as a closed-culture system – since there
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Industrial Microbiology
Fermentation processes are broadly divided into two parts viz: liquid fermentation and solid fermentation. In liquid fermentation, the microbial cells are suspended in an aqueous nutrient medium. But in solid fermentation, the microbial cells are adsorbed to a solid and nutrient rich material that supports the growth of the organism. The volume of free liquid
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Industrial Microbiology
Colony counter is a piece of equipment which is used in the microbiology laboratory to count individual colonies of microorganisms (particularly bacteria and fungi) on solid agar plates. Fully automated colony counters and manually-operated counters are available for the counting of microbes in samples or culture plates. The accurate count of bacterial colonies and cells
Autoclave is a piece of equipment that allows materials to be heat-sterilized under pressure and with a saturated steam. It is generally used to achieve sterilization of culture media and other reagents in the microbiology laboratory; and sterilization using the autoclave is achieved under pressure at various temperatures and time limit (e.g. 121oC for 15
Cork or hole borer is a piece of instrument used to create holes on solid agar media. It is an important tool required for antimicrobial susceptibility testing (AST) in the microbiology laboratory especially when performing agar well diffusion tests or determining the antimicrobial activity of a particular plant product, in which case holes are usually
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General Microbiology