QVprep Microbiology Lessons

Bacterial Growth



Zone of hydrolysis: The clear area that develops around bacterial colonies, indicating that the organism has catabolized nutrients in its vicinity, is referred to as the zone of hydrolysis. Catabolic reactions are driven by the introduction of water to break chemical bonds; hence, the development of a clear zone on certain media is an indicator of catabolism and is called a zone of hydrolysis.

Agar: The solidifying agent used in microbiological media is agar. Agar is a complex polysaccharide that is the product of a red marine algae; it is an appropriate solidifying agent because remains solid at temperatures as high as 100° C before it liquefies. Agar is a polysaccharide (carbohydrate) that is produced by red marine algae.

Fastidious microbes: A fastidious microorganism may be defined as a bacteria having complex nutritional requirements. Fastidious microbes are said to be “fussy” and will not grow if specific growth requirements are not met; the majority of bacteria do not fall into this category.

Obligate intracellular pathogens: Rickettsias and chlamydias are bacteria that are obligate intracellular pathogens. About their metabolic capabilities, this implies that microbes lack the ability to synthesize a life sustaining, metabolic compounds. Rickettsias and chlamydias have metabolic deficiencies that prevent them from living independently of a host cell.