Nutrition of the acetic acid bacteria.

Relatively little information is available on the specific nitrogen and growth factor requirements of the acetic acid bacteria. The early observation of Hoyer (1898) and of Beijerinck (1898) that only Acetobacter aceti can develop in a mineral salts-ammonium nitrogen medium with ethanol plus acetate as the source of carbon has acquired taxonomic and diagnostic value for this and, more recently, other Acetobacter species. Frateur (1950) found that acetate is unnecessary if the medium is buffered adequately with phosphates. Hoyer and Beijerinck also noted that A. xylinum and A. rancens can grow with ammonium nitrogen if glucose is added to the ethanol medium. A similar nitrogen to carbon relationship may exist for A. pasteurianum and A. kcfzingianum. These organisms are considered by Frateur to be varieties of A. rancens and to be unable to develop in a medium containing ethanol and ammonium nitrogen. Kaushal and Walker (1951), however, obtained growth of both of these organisms as well as of A. acetigenum with ammonium nitrogen in a medium containing both ethanol and glucose. Ethanol alone is adequate for the growth of A. peroxydans (Visser't Hooft, 1925; Frateur, 1950) and A. lovaniense (Frateur, 1950) with ammonium nitrogen. It is evident therefore that species other than A. aceti can utilize readily inorganic nitrogen for growth although for some strains this is possible only when glucose rather than ethanol is the source of carbon and energy. But there is another nutritional aspect which needs to be considered. The above mentioned investigations were made with media which did not contain growth factors. It has long been known that media containing complex nitrogenous materials such as yeast extracts and peptones are necessary for the growth of many species of the genus Acetobacter including A. suboxydans, A. melanogenum, and A. rancens. With the development of knowledge of the growth factor requirements of microorganisms and the availability of the active compounds in pure form, a few attempts were made to determine the specific essential nutrients supplied by the complex natural materials of the medium. Thus, Underkofler, Bantz, and Peterson (1943) showed that a strain of A. suboxydans, ATCC 621, requires pantothenic, p-aminobenzoic, and nicotinic acids for growth in a medium containing casein hydrolyzate as the source of nitrogen and glycerol as the carbon source. This made it possible for Stokes and Larsen (1945) to establish that this strain of A. suboxydans requires a mixture of six amino acids for good growth and enabled them to grow A. suboxydan for the first time in a completely defined medium. Nitrogen in the form of ammonium salts was not adequate for growth, but at suboptimum concentrations of the required amino acids, it stimulated growth. Gray and Tatum (1944), however, noted that ammonium nitrogen is sufficient for growth of a strain of A. melanogenum, M.A. 6.1, if the growth factors thiamin, and pantothenic, nicotinic, and p-aminobenzoic acids were supplied in the medium. By x-ray irradiation Gray and Tatum obtained mutants which required amino acids for growth. These results suggest that species other than A. aceti, and those previously mentioned, may be able to grow with ammonium nitrogen if supplied with essential growth factors and with an appropriate source of carbon and energy. The paucity of data on the specific growth factor and nitrogen requirements of species of the genus Acetobacter which develop only in the presence of complex nitrogenous materials prompted us to undertake the present investigations. The results obtained demonstrate that the ability to utilize ammonium nitrogen is much more widespread among the acetic acid bacteria than previously has been suspected; that a number of strains require apparently new and unidentified growth factors; and that the requirements for growth factors and nitrogen are influenced critically by the available source of carbon and energy.