Aerobic sporeforming bacilli showing the phenomenon of colony migration

Summary

It is proposed that the grouping of unicellular forms of bacteria into clusters or colonies may be the first step in the evolution of multicellular forms and that any further evolutionary advance would require the subordination of the impulses of the individual in favour of the needs of the “colony”. This latter relationship is exemplified by the group movement of certain aerobic sporeforming bacilli. A description of the nature of this movement on the surface of nutrient agar has been made.

Studies on 54 strains showing this group movement reveal that they taxonomically constitute a nebulous group in Morphological Group II of the genus Bacillus according to the presently accepted system of classification (Bergey's Manual 1957). While the large majority of the strains studied morphologically resemble B. alvei, none exhibit the typical physiological characteristics of this species. Considering all the characteristics studied, the strains in our collection could be placed in an indefinite group comprising B. alvei, B. circulans, B. laterosporus and B. pulvifaciens. This however does not reflect any marked dissimilarities between the strains studied but rather the unsatisfactory taxonomy of the species enumerated. A re-examination of the determinative classification of these four species especially with reference to the unsatisfactory use of starch hydrolysis in the key to the genus is suggested.