CHELATING AGENTS IN GROWTH INITIATION OF BACILLUS GLOBIGII

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Abstract
Several filter-sterilized compounds were tested for capacity to substitute for the stimulatory effect of autoclaved glucose and phosphate (GP) on growth initiation of B. globigii in a filtered, chemically-defined medium. Activity was detected in many compounds unrelated in chemical structure or known biochemical function. All active compounds, like the GP factor, are characterized by activity maxima with inhibition zones of concentration excess. The activity maxima range from about 1 [mu]g per ml (e.g., salicylaldehyde) to as high as 10,000 [mu]g (malic acid). Some compounds were characterized by narrow concentration ranges of activity (e.g., salicylaldehydr, gallic acid), a few by a relatively broad range (kojic acid, oxalic acid). Active compounds included 2-hydroxy-derivatives of benzoic acid and benzaldehyde, 3-hydroxy-gamma-pyrones (kojic and meconic acids, but not chelidonic acid), alpha-hydroxy- and alpha-thiol aliphatic polyfunctional acids (glycolic, thioglycolic, malic, thiomalic, etc.), certain pyridine derivatives (pyridoxal, substituted picolinic acids), and some miscellaneous compounds (e.g., citric, ascorbic and quinic acids). The only property seemingly common to these active compounds is their capacity to chelate metal ions although many known chelating compounds are inactive. This function also is suggested by the observation that although B. globigii required Mn++ for optimum growth, effective concentrations of the ionic form delay growth initiation in the absence of adequate GP factor. It is postulated that GP factor and other active substances function as specific metal carriers, providing the cell with a nontoxic, controlled level of assimilable metals.