Nutrition and Media

Recent intersections between geology and microbiology, as well as environmental engineering and microbiology, have provided even more creative approaches for developing selective media for novel organisms. This chapter places some emphasis on the nutritional needs of some of the broad groups of prokaryotes that have been discovered through using selective media as an enrichment tool. Other important aspects of nutrition that are considered in the chapter are requirements for vitamins, trace minerals, other growth factors, buffers to control pH, sterilization, and preparation of solid media. The essential nutritional requirements for prokaryotes can be divided into two classes: macronutrients and micronutrients. More than 30 elements are considered essential for cell growth; however, there are six nonmetals (carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus) and two metals (potassium and magnesium) that constitute 98% of the dry weight of prokaryotic organisms. Sodium is necessary for certain marine bacteria, phototrophs, and some anaerobes. Mixed hydrolysates are processed yeast or meat extracts to supplement the nutritional aspects of peptones by providing some amino acids, carbohydrates, nucleic acid fractions, organic acids, vitamins, and trace minerals lost during their manufacture. It is important to ensure that the blood and serum used in formulating bacteriological media are free of pathogens and potential health risks, especially in light of the recent bovine spongiform encephalopathy outbreaks.