Field of Science

Nocardia pseudovaccinii

As noted on this site before, the Actinobacteria are one of the most significant groups of bacteria in the terrestrial environment. Among the more diverse genera of Actinobacteria is Nocardia, members of which produce fine, branching mycelia that often fragment into individual rod-shaped or coccoid segments, each of which is capable of developing into a new mycelium (Goodfellow et al. 2012). As is the way of things, Nocardia species are usually soil dwellers but are more commonly studied as facultative pathogens. Nevertheless, recent years have seen the recognition of an increasing number of species isolated from soil samples with one such species being Nocardia pseudovaccinii.

Nocardia pseudovaccinii was described as a new species by Kim et al. (2002). In culture, N. pseudovaccinii grows a beige-red substrate mycelium supported a scarce, white aerial mycelium. Kim et al. (2002) identified the species as able to utilise a wide range of organic substrates such as ribose and glucosaminic acid though it could not break down others such as sucrose or citrate. Molecular analyses of Nocardia in Kim et al. (2002) and Goodfellow et al. (2012) do not really indicate a clear association of N. pseudovaccinii with any other species. Bacterial systematists apparently still maintain that neighbour-joining analyses are something more than a complete waste of time. I do not support this view.

The strains assigned to N. pseudovaccinii by Kim et al. (2002) had previously been identified as another species, N. vaccinii, hence the new species' name ('vaccinii', in case you were wondering, has no direct connection to vaccines but refers to Vaccinium, the plant genus including blueberries and from which N. vaccinii was first isolated). Nocardia vaccinii has been known to act as a facultative plant pathogen but I am not aware of this role being identified for N. pseudovaccinii. The original isolates were cultured from soil (though Kim et al. say nothing about what kind of soil or even where it was sampled). Nocardia pseudovaccinii has also been found forming part of the microbiome of wireworms of the genus Agriotes, beetle larvae that feed on plant roots. It may form a symbiotic association with these grubs that provides the latter with antibiotic protection from the pathogenic fungus Metarhizium brunneum (Kabaluk et al. 2017). A good thing for the wireworms but perhaps not so good for agriculturists who would like to keep them under control.

Goodfellow, M., P. Kämpfer, H.-J. Busse, M. E. Trujillo, K. Suzuki, W. Ludwig & W. B. Whitman (eds) 2012. Bergey's Manual of Systematic Bacteriology 2nd ed. vol. 5. The Actinobacteria, Part A and B. Springer.

Kabaluk, T., E. Li-Leger & S. Nam. 2017. Metarhizium brunneum—an enzootic wireworm disease and evidence for its suppression by bacterial symbionts. Journal of Invertebrate Pathology 150: 82–87.

Kim, K. K., A. Roth, S. Andrees, S. T. Lee & R. M. Kroppenstedt. 2002. Nocardia pseudovaccinii sp. nov. International Journal of Systematic and Evolutionary Microbiology 52: 1825–1829.

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