Soil enrichment for the isolation of sporangial subgroup II Bacillus species, and observations concerning a coil-forming member of this group

Abstract

Enrichment culture procedures are described which allow recovery from soil of mainly sporangial subgroup II Bacillus species, subgroup I plus subgroup II, or the latter plus a coil-forming member of subgroup II. After isolation, the coil-forming type grew normally and sporulated extensively only on agarized soil medium. Growth was normal on soil extract agar but sporulation was less extensive. Limited sporulation occurred when divalent cations were added to more conventional media. Normal vegetative growth occurred on other media investigated only when the pH value was held within relatively narrow limits. The presence of carbohydrate in agar media caused partial growth inhibition, a lack of catalase activity, and the formation of very long coiled cells plus pleomorphic cells, whereas overt cell lysis occurred in vigorously shaken broth cultures. These responses possibly reflect an unbalanced growth condition caused by growth at pH extremes, and not by carbohydrate per se. The characteristic features that set the coil-forming bacilli apart from other subgroup II Bacillus species were shown to be (1) their inability to grow at pH values below 6.5, (2) their inability to ferment carbohydrates, (3) their high oxygen requirement for growth, and (4) their ability to reduce thiosulfate to H2S. In addition, these bacilli can be distinguished from closely related established species by other biochemical tests.