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 degrees C and in the presence of NaCl (3 %), cephaloridine (10 microg ml(-1)) and gentamicin sulphate (10 microg 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.