Bacillus pulvifaciens (N. SP.), an organism associated with powdery scale of honeybee larvae.

In a recent investigation on the cause of death of honeybee larvae it was observed (le Maistre, 1949) that cells of the honeycomb contained scale (thin, dried remnants of dead larvae) that was dry, powdery, and light brown in color, and therefore quite unlike scale resulting from European and American foulbrood diseases. Comb with this unusual scale was sent to Ottawa for further study. Microscopic examination of the powdery material revealed many large spores with thick walls and fairly numerous short rods. Samples of this powdery material were removed aseptically into sterile water and loopfuls streaked or plated in appropriate dilutions with yeast beef agar; portions were also heated for 10 minutes at 80 C prior to plating. After two days' incubation at 33 C every sample yielded a pure culture of an organism that produced colonies varying from Brazil red (Ridgway, 1912), to brownish-orange, to light brown in color; all colonies examined showed a rather short, well-stained, gram-positive rod. After 5 to 8 days' incubation these colonies yielded large oval spores identical with those originally found in the powdery scale. Another phenomenon was observed at this time; many of the pigmented colonies and of the cultures isolated from these showed at their periphery much lighter and even creamy whitish growth. When cultures were transferred to fresh medium or streaked on fresh plates both deeply pigmented and whitish colonies appeared. After suitable incubation all cultures showed short gram-positive rods and after further incubation typical and similar spores. It was also observed that after several transfers on yeast beef agar the cultures began to lose their pigment and spore-producing capacity. However, by culturing on the pollen extract medium of Smith et al. (1949) and on glucose agar these characteristics were retained. The procedure outlined in the key for aerobic mesophilic sporeforming bacteria by Smith et al. (1946) was used for identification, after repurification of the cultures. The organism forms spores in definitely swollen sporangia; produces acid but no gas from glucose; does not hydrolyze starch, does not produce acetylmethylcarbinol, nor utilize citrates; and lowers the pH of glucose proteose peptone broth to 6.0 to 6.4. According to these characteristics, the organism corresponds with Bacillus laterosporus; however, other characteristics are quite different as the following detailed description will show: The vegetative rods are 0.3 Ju to 0.6 ,& by 1.5 ,u to 3.0 ,, with rounded, not pointed ends; on nutrient agar motility is restricted to a small proportion of cells