A Probability Matrix for Identification of some Streptomycetes

Abstract

The character state data obtained for clusters defined at the 77.5% SSM similarity level in the phenetic numerical classification described by Williams et al. (1983) were used to construct a probabilistic identification matrix. The 23 phena included were the major clusters (19 Streptomyces, 2 Streptoverticillium and 'Nocardia' mediterranea) and one minor cluster (Streptomyces fradiae). The characters most diagnostic for these clusters were selected using Sneath's CHARSEP and DIACHAR programs. The resulting matrix consisted of 41 characters x 23 phena. Identification scores, determined by Sneath's MATIDEN program were used to evaluate the matrix. Theoretical assessment was achieved by determination of the cluster overlap (OVERMAT), the identification scores for the Hypothetical Medium Organism of each cluster (MOSTTYP), and the scores for randomly selected cluster representatives using the classification data of Williams et al. (1983). The matrix was evaluated practically by the independent re-determination of the characters for the same cluster representatives, which also provided a measure of test error. Finally it was used to identify unknown isolates from a range of habitats. The results showed that the matrix was theoretically sound. Test error was within acceptable limits and did not distort identifications. Of the unknown isolates, 80% were clearly identified with a cluster. It is suggested that the matrix could form the basis for a more objective identification and grouping of the large number of Streptomyces species which have been described.

Isolation and characterization of potential antibiotic producing actinomycetes from water and sediments of Lake Tana, Ethiopia

“…Antagonistic activity of isolates against Gram negative and Gram positive bacteria was primarily screened by using perpendicular streak method and later evaluated by agar overlay method [28,30] . In perpendicular streak method, nutrient agar media was used and each plate was streaked with individual isolates at the center/diameter of the plate and incubated at 30 °C for 7 d. Later, 24 h fresh sub-cultured test bacteria were prepared and streaked perpendicular to the isolates and incubated at 37 °C for 24 h [30] . In agar overlay method, [5][6][7] d old colony of actinomycetes was spot inoculated on nutrient agar plates and incubated for 7 d at 30 °C .…”

“…The isolates of LT003, LT010 and LT005 showed maximum zone of inhibition i.e., 24 mm, 22 mm and 20mm respectively against P. aeruginosa. The isolate LT005 was observed with maximum zone of inhibition (30 mm) against S. typhi (Table 2). …”

Diversity of streptomycetes among specific Greek terrestrial ecosystems

“…Cluster group Willcox probability range of scores* Williams et al 1983b. †Numbers in parenthesis indicate the number of habitats where streptomycetes species were detected.…”

“…Identification of indigenous soil isolates from the seven different soil samples was carried out using 41 morphological and physiological diagnostic characters contained in the probabilistic identification matrix of Williams et al (1983b). Three identification statistics were used to assess the reliability of the identification of unknown strains: the Willcox probability, taxonomic distance and its standard error (Williams et al 1983b).…”

“…Streptomyces strains have been isolated from diverse Greek areas and were identified using the probabilistic identification scheme of Williams et al (1983b). Differences in cluster groups diversity among the different areas have been estiCorrespondence to : Dr A.D. Karagouni, Microbiology Laboratory, Section of Botany, Biology Department, University of Athens, 15781 Athens, Greece (e-mail: akarag@cc.uoa.gr).…”