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Deoxyribonucleic acid-deoxyribonucleic acid reassociation and deoxyribonucleic acid-ribosomal ribonucleic acid cistron similarity studies showed that the anaerobic, gram-positive cocci comprise a rather heterogeneous group of bacteria. The deoxyribonucleic acid-ribosomal ribonucleic acid hybridization studies distinguished seven groups. Groups 1 and 2 consisted of Peptostreptococcus magnus and Peptostreptococcus prevotii, respectively. Peptostreptococcus asaccharolyticus ATCC 14963T (T = type strain) and Peptostreptococcus indolicus ATCC 29427T formed a third group, and Peptostreptococcus asaccharolyticus DSM 20364 together with Hare group VIII strain NCTC 9820 formed group 4. Peptostreptococcus anaerobius DSM 20357 was more closely related to Eubacterium tenue ATCC 25553T and Clostridium lituseburense ATCC 25759T than to any of the other species studied. Peptostreptococcus micros strains DSM 2046gT and DSM 20367 together with strains belonging to Hare group IX formed group 6, and group 7 consisted of Peptostreptococcus pawulus DSM 20469T. Strains of different Hare groups were all assigned to one of the seven groups or to the genus Staphylococcus (Hare group VIIb strain NCTC 9819) or the genus Streptococcus (Hare group VIa strain NCTC 9806). The anaerobic cocci also have a diversity of murein structures. This is the first report showing that strains belonging to the same species have different murein types.

Plasmid pHF360 was constructed from cloned rRNA genes (rDNA) of Pseudomonas aeruginosa and used as hybridization probe for the Pseudomonas fluorescens group. The probe was tested by dot and in situ colony hybridizations to chromosomal DNAs from a wide variety of organisms. pHF360 DNA hybridized exclusively to chromosomal DNAs from bacteria representing the P. fluorescens group and separated them clearly from all other bacteria tested in the present study. Determination of the nucleotide sequence of the cloned DNA showed that it is a fragment from a 23S rRNA gene of P. aeruginosa. It was compared with the published 23S RNA sequence from Escherichia coli.