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The simultaneous addition of phosphate with 2,4-D enhances the toxicity of the latter to A. vinelandii. This enhanced toxicity is related to the magnesium concentration of the environment. The microbiology of coal has received little attention by comparison with the large amount of research on petroleum. Coal is a much more complex organic material than petroleum and probably consists of condensed rings of an aromatic and hydroaromatic nature. The ring systems in coal resist microbial oxidation; only the highly oxidized coals give any indication of supporting an indigenous microflora (Lieske and Hofmann 1928). For this reason a study of the microbial attack on polynuclear hydrocarbons was initiated as a means of investigating the constitution of coal. The higher polynuclear hydrocarbons serve as model compounds in determining the products of microbial oxidation of highly condensed ring systems. Coal contains phenolic-hydroxyl and is thought to contain quinone and carboxyl groups. The demonstration that these substituent groupings appear in the intermediate products of polynuclear hydrocarbon oxidation may help to explain their presence in coal. Study of these compounds should also aid in determining the effects of steric configuration, substitution, size of the molecule and other physical and chemical factors on the resistance of the compounds to microbial attack. It may be possible to draw analogies from such studies to explain the relative resistance of a material like coal to microbial attack. We have chosen phenanthrene as one such model compound. The attack of phenanthrene by soil bacteria has been reported by Tausson (1928b, 1929), who also described its utilization by certain anaerobic sulfate-reducing bacteria (Tausson and Vesselov, 1934). In an earlier study Tausson (1928a) described two new species, Bacillus phenanthrenicus bakiensis and B. phenanthrenicus guricus, which in pure culture could assimilate phenanthrene. Sisler and ZoBell (1947) noted that marine bacteria assimilated phenanthrene and anthracene more rapidly than naphthalene, or the higher homologues 1,2-benzanthracene and 1,2,5, 6-dibenzanthracene. No intermediates in the oxidations were isolated in these studies; naphthalene is the largest polynuclear hydrocarbon whose oxidation has been studied in detail. The present experiments were initiated to study the dissimilation of phenanthrene by pure cultures of bacteria, and to determine the intermediate products in the oxidative pathway.

EXCRETION BY STREPTOMYCETES OF FACTORS CAUSING FORMATION OF AERIAL HYPHAE BY OLD CULTURES