A relatively high proportion of the indigenous bacteria of a field soil (27.1%, corresponding to 14.1 millions/g.) required one or more vitamins for growth. The vitamins found to be essential, either alone or with others, were, in order of frequency, thiamine, biotin, vitamin B12, pantothenic acid, folic acid, nicotinic acid, and riboflavin. In all, 16 different 'patterns' were noted for vitamin requirements, the number of vitamins needed by individual strains ranging from one to five. The findings point to the soil as an important habitat of vitamin-requiring bacteria, many of which show potentiality as assay organisms. Their occurrence in the numbers found indicates that growth-factors should receive equal emphasis with antibiotics in problems involving the microbial equilibrium in soil and interrelationships between the normal soil microflora, soil-borne disease organisms, and growing plants.

Comparative studies of the relative incidence of bacterial types occurring in the rhizosphere of different plants and in control soils indicated that the qualitative nature of the soil microflora is markedly influenced by the growing plant. In the rhizosphere Gram-negative rods are proportionately increased while Gram-positive rods, coccoid rods, and spore-forming types are relatively less abundant.The majority of bacteria isolated from soil by non-selective plating are forms included in the family Proactinomycetaceae (Jensen's classification). Of these by far the largest group consists of members of the genus Corynebacterium. In the rhizosphere proactinomycetes as a whole are relatively less abundant, with the Corynebacterium (non-motile) group likewise depressed. However, closely related motile forms classed as Mycoplana are preferentially stimulated.In the rhizosphere the bacteria show definitely greater physiological activity than in soil distant from the plant. Not only is there a notably greater proportion of motile forms, and a pronounced increase in the incidence of chromogenic types, but also a higher incidence of liquefying bacteria and of those able to affect glucose.A comparison of the rhizosphere of certain plant varieties resistant and susceptible respectively to soil-borne disease showed differences of a qualitative nature in the bacterial flora suggestive of a greater "rhizosphere effect" in the case of the susceptible varieties studied. Results point to the possibility that resistance may be associated with a selective action of root excretions on the saprophytic soil microflora.

A study was made of organisms concerned with the red discoloration of salted hides, also termed "red heat", which defect may occasion loss in the leather industry through spotting and weakening of the fibre. Red halophilic sarcinae were isolated from Argentine hide. From Canadian hides showing red discoloration, two species of pleomorphic rods were isolated as active agents. One of these, occurring on salted cowhides, was found to be similar to Serratia salinaria (Harrison and Kennedy) Bergey et al., a source of reddening of cured codfish in eastern Canada. The other organism causing discoloration, isolated from buffalo hide, was regarded as a new species and designated Serratia cutirubra n.sp. Both of these halophilic organisms, owing to their proteolytic action, are considered capable of greater damage to hides than the red sarcinal types which are non-liquefying, and which may also be present on Canadian hides. Non-chromogenic halophilic bacteria were also isolated from discolored hides. These develop at a lower salt concentration range than the red organisms and are probably less active in causing injury to fibre in well salted hides.

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