Patrick Grimont

Taxonomy of the genus serratia

One hundred and fifty-six strains of Serratia and related bacteria including representatives of Enterobacter liquefaciens, Enterobacter cloacae, Enterobacter aerogenes, Erwinia carotovora, Erwinia chrysanthemi, Erwinia herbicola and Erwinia nimipressuralis were studied using 223 morphological, physiological, biochemical and carbon source utilization tests. The results were subjected to computer analysis. At the 80% similarity level all strains, except two, grouped into eight phenons representing: (A) Serratia marcescens with the neotype CCM303 (ATCCI3880); (B) S. marinorubra with the monotype NCTC10912 (ATCC27614); (CI) S. liquefaciens with the type ATCCI4460; (C2) S. plymuthica with the monotype CCM640 (ATCC183); (D) Erwinia herbicola with the neotype of Enterobacter agglomerans NCTC9381; (E) Enterobacter cloacae with the neotype NCTCI0005 and Erwinia nimipressuralis; (F) Erwinia carotovora with the type ATCC495, Erwinia atroseptica and Erwinia chrysanthemi; (G) Klebsiella mobilis with the neotype NCTCI0006. At the 70% similarity level the phenons formed two groups: (A, B, CI, C2) and (D, E, F, G). The following conclusions were drawn. (I) There are three species of enterobacteria producing prodigiosin: S. marcescens, S. plymuthica and S. marinorubra. (2) There are four species of Serratia, one colourless (S. liquefaciens). (3) Subphenons (biovars) are described within the four species of Serratia. (4) Non-pigmented wild-type strains of S. marcescens can generally be differentiated from pigmented strains by characters other than pigmentation, because subphenons are homogeneous with respect to pigmentation. This survey raised some problems of nomenclature because old descriptions could be found that could loosely fit the present phenons. Comparison with an authentic culture was considered to be the most objective way of identifying these phenons with earlier named species.

Deoxyribonucleic Acid Relatedness Between Serratia plymuthica and Other Serratia Species, with a Description of Serratia odorifera sp. nov. (Type Strain: ICPB 3995)

Seven new isolates of Serratia plymuthica (including two from a human source) and 24 isolates resembling unclustered Serratia strain 38 (Grimont et al., J. Gen. Microbiol 98:39-66, 1977) are described. Deoxyribonucleic acid relatedness studies, obtained with labeled reference deoxyribonucleic acid from S. plymuthica 392 confirm that S. plymuthica is a discrete species. Mean percent relatedness of S. plymuthica isolates to strain 392 was 88 ± 13.6 (standard deviation), whereas the mean percent relatedness of S. liquefaciens isolates (the closest species) to strain 392 was 52 ± 12.4. Strain 38 and twenty-four “38-like“ isolates constitute a new deoxyribonucleic acid hybridization group that is 28 to 43% related to Serratia species and to the “Citrobacter-like” group of Leclerc and Buttiaux, and 15 to 22% related to other known species of Enterobacteriaceae. This 38-like group constitutes a new species that is named Serratia odorifera sp. nov. (type strain, ICPB 3995). Two biotypes (1 and 2) are described. Strains of this species will grow on caprylate-thallous agar (selective for Serratia spp.), and they have a characteristic odor. Most strains of S. odorifera were recovered from clinical specimens.

Brochothrix campestris sp. nov.

Two deoxyribonucleic acid hybridization groups were found among Brochothrix strains isolated from various sources. One genospecies contained 165 strains and included the type strain of Brochothrix thermosphacta. The other genospecies (five strains) represented a new species, for which the name Brochothrix campestris sp. nov. is proposed. The type strain is strain S3 (= CIP 102920 = ATCC 43754). B. campestris differs from B. thermosphacta by growth in the presence of 8 and 10% NaCI and 0.05% (wt/vol) potassium tellurite, by hippurate hydrolysis, and by acid production from rhamnose.

Phenotypic diversity of anaerobic glycerol dissimilation shown by seven enterobacterial species.

The anaerobic glycerol pathway was studied in seven enterobacterial species selected as representative of different behaviours in terms of anaerobic glycerol dissimilation. The presence of oxidative and reductive pathways of the dha regulon in Klebsiella pneumoniae enabled the cells to grow fermentatively on glycerol. The first two enzymes of the dha regulon (glycerol dehydrogenase type I and dihydroxyacetone kinase) represent the oxidative branch, while the latter two (glycerol dehydratase and 1,3-propanediol dehydrogenase) represent the reductive branch of glycerol fermentation. The slower utilization of glycerol by K. oxytoca was attributed to low production of 1,3-propanediol. K. oxytoca lacked glycerol dehydratase and demonstrated low 1,3-propanediol dehydrogenase activity. K. planticola and K. ozaenae differed from K. pneumoniae and K. oxytoca in lacking the ability to grow on glycerol. K. planticola lacked both enzymes of the reductive branch of glycerol fermentation, and K. ozaenae possessed glycerol dehydrogenase only. K. rhinoscleromatis and Hafnia alvei, like Escherichia coli, did not possess a dha regulon. The glycerol dehydrogenase type II of H. alvei was distinct from that of E. coli. The phenotypic diversity of anaerobic glycerol dissimilation may have taxonomic applications.