Humic and fulvic acids stimulate the growth of Mycobacterium avium

Mycobacterium avium, an environmental, opportunistic pathogenic mycobacteri um, has been isolated frequently and in high numbers from waters in Finland and from acid, brown water swamps of the southeastern coastal USA. M. aviu m has also been recovered in high numbers from Finnish drinking water and f requently isolated from Finnish AIDS patients. Boreal forests and brown wat er swamps are similar in that they are rich in humic and fulvic acids and o f low pH and dissolved oxygen. Growth of representative isolates of M. aviu m in natural water was stimulated markedly by the addition of humic and ful vic acids. Further, the M. avium isolates grew at pH levels as low at 4.0 a nd at oxygen levels equal to 4% of atmospheric levels. The high numbers of M. avium in boreal waters and brown water swamps are likely due to their ab ility to proliferate in those humic- and fulvic-rich, acidic, micro-aerobic environments. (C) 1999 Federation of European Microbiological Societies. P ublished by Elsevier Science B.V. All rights reserved.