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Aims:  To assess the antibiotic biosynthetic potential of Amycolatopsis sp. strain UM16 and eight other Amycolatopsis species. Methods and Results:  Amycolatopsis genomic DNA was screened by PCR for the glycopeptide, Type‐II (aromatic) polyketide and ansamycin biosynthetic gene clusters. Amycolatopsis sp. strain UM16, which exhibits weak antitubercular activity, was shown to have the glycopeptide oxyB gene and the Type‐II (aromatic) polyketide‐synthase KSα‐KSβ tandem gene pair, but not the AHBA synthase gene. The ristocetin (glycopeptide) producer, Amycolatopsis lurida NRRL 2430T, was shown to have the oxyB gene and the Type‐II polyketide‐synthase KSα‐KSβ tandem gene pair. Amycolatopsis alba NRRL 18532T was shown to have the glycopeptide oxyB gene and the AHBA synthase gene. Phylogenetic analyses using Amycolatopsis oxyB and KSα‐KSβ gene sequences were conducted. Conclusions:  Amycolatopsis sp. strain UM16 appears to have the biosynthetic potential to produce glycopeptide and Type‐II polyketide antibiotics, but not ansamycins. The potential to synthesize aromatic polyketides may be more widely distributed in Amycolatopsis than is currently recognized. Significance and Impact of the Study:  PCR screening is a very useful tool for rapidly identifying the biosynthetic potential of an antibiotic‐producing actinomycete isolate. Advanced knowledge of the type of antibiotic(s) produced will allow appropriate methods to be selected for antibiotic purification.

Two novel nocardioform actinomycetes, strains Q41T and HMC25T, were isolated from soil samples collected in the Western Cape province, South Africa. Rapid genus identification revealed that the isolates belonged to the genus Kribbella (based on single-digestion restriction analysis of the 16S rRNA gene sequences with MboI, VspI, SphI, SnaBI, SalI and AgeI). Both isolates had ll-diaminopimelic acid and glycine in their cell-wall peptidoglycan, and contained mannose and ribose as whole-cell sugars. Strain HMC25T is able to grow at 45 °C and in the presence of NaCl (3 %), cephaloridine (10 μg ml−1) and gentamicin sulphate (10 μg ml−1). Strain Q41T grows in the presence of NaCl (2 %). Neither strain was able to grow under anaerobic conditions, whereas Kribbella flavida KACC 20248T, Kribbella jejuensis HD9T, Kribbella koreensis KACC 20250T and Kribbella sandramycini KACC 20249T exhibited weak but distinct growth under anaerobic conditions. Physiological test results and 16S rRNA gene sequence analysis allowed Q41T and HMC25T to be distinguished from other members of the genus with validly published names. Strains HMC25T (=NRRL B-24426T=DSM 17345T) and Q41T (=NRRL B-24425T=DSM 17344T) therefore represent the type strains of novel species, for which the names Kribbella swartbergensis sp. nov. and Kribbella karoonensis sp. nov., respectively, are proposed.

A novel actinomycete, strain HMC10(T), was isolated from a soil sample taken from the banks of the Gamka River in the Swartberg Nature Reserve, Western Cape Province, South Africa. Strain HMC10(T) was identified as a member of the genus Nonomuraea by a polyphasic approach. Strain HMC10(T) could be differentiated from other members of the genus Nonomuraea on the basis of physiology and 16S rRNA gene sequence analysis. DNA-DNA hybridization further differentiated strain HMC10(T) from its nearest phylogenetic neighbour, Nonomuraea turkmeniaca NRRL B-16246(T) (4.5 +/- 3.8% DNA relatedness). Strain HMC10(T) exhibited weak antibiosis against Mycobacterium aurum A+, but none against Mycobacterium tuberculosis H37Rv(T). The name Nonomuraea candida is proposed, with the type strain HMC10(T) (= DSM 45086(T) = NRRL B-24552(T)).

As part of an antibiotic-screening programme, the actinomycete strain HMC1T was isolated from soil collected from the banks of the Gamka River in the Swartberg Nature Reserve, Western Cape Province, South Africa. The isolate produced branching vegetative mycelia, which entwined to form rope-like structures. It exhibited antibiosis against Enterococcus faecium VanA (a vancomycin-resistant clinical strain) and Mycobacterium aurum A+. Organic solvent extracts of the culture filtrate and mycelial mass of strain HMC1T exhibited moderate antibiosis against Mycobacterium aurum A+, Mycobacterium bovis BCG (Tokyo) and Mycobacterium tuberculosis H37RvT. The chemotaxonomic characteristics of strain HMC1T corresponded with those of members of the genus Actinomadura. Furthermore, phylogenetic analysis based on the 16S rRNA gene showed that the strain was closely related to members of the genus Actinomadura. Phenotypic and 16S rRNA gene sequence analyses indicated that strain HMC1T represents a novel species of the genus Actinomadura, for which the name Actinomadura rudentiformis sp. nov. is proposed. The type strain is HMC1T (=DSM 44962T=NRRL B-24458T).