Growth Studies with Microorganisms

Pantothenic acid and biotin were thus found to be growth factors for yeast. Like riboflavin these molecules are incorporated into larger molecules in order to exert their essential metabolic function. Unlike the other vitamins there has been no evidence of pathological signs in man which can be attributed to dietary deficiencies in biotin or pantothenic acid. 

Similar experiments by Lwoff showed nicotinic acid was an essential growth factor for Hemophilus bacteria and also for Staph, aureus. By the 1940s an aphorism had been coined Growth factors for microorganisms are B vitamins for higher animals.  

The introduction of techniques for mutagenesis by UV irradiation or by the use of chemicals considerably extended the applications of microbial studies to nutrition (Davis, 1954-1955). Auxotrophic mutants were produced with nutrient dependencies not shown in the untreated parental strains (Beadle and Tatum, 1940). The fortuitous discovery of penicillin by Fleming and its successful use in the treatment of infections (Florey) promoted exhaustive research into its mode of action. Eventually it was established that penicillin prevented the proliferation of gram-positive bacteria by blocking the synthesis of their cell walls 

By definition all hormones affect the behavior of their target cells. Examples of the interplay between endocrine disturbances and their biochemical consequences are provided by some of the diseases of the thyroid, which directly affects basal metabolic rate, and diabetes mellitus, where glucose metabolism is deranged. 

In 1858 Schiff removed the thyroid gland from animals and found they could not survive. From his, and later, Horsley s, experiments and from the clinical observations it was concluded that the effects of removal or damage to the thyroid were due to a loss of its internal secretions. Confirmation of this came when patients with myxoedema were successfully treated by thyroid extracts or even by eating thyroid tissue. 

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Previous studies have investigated batch fermentation of both carbon sources and microorganisms. The microorganisms will accumulate PHAs after the cell reached the maximum growth coupled with the depletion of nitrogen or phosphorus (Braunegg et al 1998 Wang Bakken, 1998 Chien et al, 2007). 

The importance of zinc to growth and development in all forms of life was first established through zinc deficiency studies of microorganisms followed by those in plants and animals see Nutritional Aspects of Metals Trace Elements) The involvement of zinc in a wide variety of metabolic processes including carbohydrate, lipid, protein, and nucleic acid synthesis and degradation paralleled the technical advances in analytical methods that could detect the presence of zinc in minute amounts coupled with advances in the methodology for protein isolation and purification. 

The majority of ecotoxicological data for individual strains of soil microorganisms was derived from studies with amended growth media or soil slurries therefore, these data cannot be used directly to infer the exposure effects in aerobic soil because the... 

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