Skip to main content
ARS Home » Research » Publications at this Location » Publication #83547

Title: BACILLUS PSEUDOMYCOIDES SP. NOV. NOM. REV.

Author
item Nakamura, Lawrence

Submitted to: International Journal of Systematic and Evolutionary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: The validity of the innocuous bacterium called Bacillus mycoides has been questioned because its description is almost identical to that of another bacterium called Bacillus thuringiensis. Because Bacillus thuringiensis is frequently used in insecticidal preparations, new highly active isolates are constantly being sought. It is of academic and practical interest to learn exactly how B. mycoides should be classified. Academically, the relationship of B. mycoides to the other Bacillus species would be important to know, and practically, knowing what kinds of innocuous organisms exist would be helpful in making correct identification of possible insecticidal organisms. Study of its genetic and biochemical characteristics showed that B. mycoides is composite of two separate species, one being the species proper and the other an unknown species. The results showed that the unknown is distinctively different from other Bacillus species. Therefore, the unknown was named as the new species Bacillus pseudomycoides.

Technical Abstract: Previous DNA relatedness studies showed that strains identified as Bacillus mycoides segregated into two genetically distinct yet phenotypically similar groups, one being B. mycoides sensu stricto and the other an unclassified taxon. In the present study, the taxonomic position of this second group was assessed by measuring DNA relatedness spectrophotometrically and observing phenotypic characteristics of an increased number of B. mycoides strains. Also determined was the second group's 16S RNA gene DNA sequence. The 36 B. mycoides strains studied segregated into two genetically distinct groups showing relatedness of about 30%; 18 strains represented the species proper and 18 the second group with intragroup DNA relatedness ranging from 70 to 100%. DNA relatedness to the type strains of presently recognized species with G+C contents of approximately 35 mol% (B. alcalophilus, B. cereus, B. circulans, B. lentus, B. megaterium, and B. sphaericus) ranged from 22 to 33%. Although two B. mycoides groups were shown to be genetically distinct taxa, a high similarity of 98% was noted for their 16S RNA sequences. Further analyses showed that both B. mycoides and the second group formed a tight cluster with B. cereus. The data have established that the second B. mycoides group merits recognition as a new species for which the name Bacillus pseudomycoides is proposed.