Biosurfactant Production by Mycolic Acid-Containing Actinobacteria

The Actinobacteria produce an array of valuable metabolites including biosurfactants which are gaining increased attention in the biotechnology industries as they are multifunctional, biorenewable and generally superior to chemically synthesized compounds. Biosurfactants are surface-active, amphipathic molecules present at the microbial cell-surface or released extracellularly and in a variety of chemical forms. The mycolic acid-containing actinobacteria (MACA), classified in the order Corynebacteriales, represent a potentially rich source of biosurfactants for novel applications and undiscovered biosurfactant compounds. Members of the mycolate genus Rhodococcus produce various well-characterised glycolipids. However, other mycolate genera including Corynebacterium, Dietzia, Gordonia and Tsukamurella although less extensively investigated also possess biosurfactant-producing strains. This chapter captures current knowledge on biosurfactant production amongst the MACA, including their chemical structures and producer organisms. It also provides an overview of approaches to the recovery of biosurfactant producing MACA from the environment and assays available to screen for biosurfactant production. Methodologies applied in the extraction, purification, and structural elucidation of the different types of biosurfactants are also summarised. Potential future applications of MACA-derived biosurfactants are highlighted with particular focus on biomedical and environmental possibilities. Further investigation of biosurfactant production by MACA will enable the discovery of both novel producing strains and compounds with the prospect of biotechnological exploitation

Dispelling the "Nocardia amarae" myth: a phylogenetic and phenotypic study of mycolic acid-containing actinomycetes isolated from activated sludge foam.

Right-angle branched filaments and rods micromanipulated from activated sludge foam and mixed liquor were identified as putatively novel members of the genera Gordonia, Mycobacterium and Rhodococcus using a combination of chemical, molecular and morphological data. Pyrolysis mass spectrometric analyses of gordoniae isolated in both the present and a previous study revealed pyro-groups, distinct from validly described Gordonia species, which could be equated with those based on morphological properties and 16S rDNA data. Putative gordoniae assigned to one of these groups were found to be closely related to strains currently identified as "Rhodococcus australis". These strains were also found to have properties consistent with their classification in the genus Gordonia. The results of this study highlight the limitations of the microscopic approach to filament identification and cast further doubt on the view that foaming can be attributed to members of one or a few Nocardia species

Gordonia defluvii sp. nov., an actinomycete isolated from activated sludge foam.

Three strains of non-motile, Gram-positive, filamentous actinomycetes, isolates J4T, J5 and J59, initially recognized microscopically in activated sludge foam by their distinctive branching patterns, were isolated by micromanipulation. The taxonomic positions of the isolates were determined using a polyphasic approach. Almost-complete 16S rRNA gene sequences of the isolates were aligned with corresponding sequences of representatives of the suborder Corynebacterineae and phylogenetic trees were inferred using three tree-making algorithms. The organisms formed a distinct phyletic line in the Gordonia 16S rRNA gene tree. The three isolates showed 16S rRNA gene sequence similarities within the range 96.9–97.2 % with their nearest phylogenetic neighbours, namely Gordonia bronchialis DSM 43247T and Gordonia terrae DSM 43249T. Strain J4T was shown to have a chemotaxonomic profile typical of the genus Gordonia and was readily distinguished from representatives of the genus on the basis of Curie-point pyrolysis mass spectrometric data. The isolates shared nearly identical phenotypic profiles that distinguished them from representatives of the most closely related Gordonia species. It is evident from the genotypic and phenotypic data that the three isolates belong to a novel Gordonia species. The name proposed for this taxon is Gordonia defluvii sp. nov.; the type strain is J4T (=DSM 44981T=NCIMB 14149T)

Millisia brevis gen. nov., sp. nov., an actinomycete isolated from activated sludge foam.

The taxonomic position of two mycolic-acid-producing actinomycetes, isolates J81T and J82, which were recovered from activated sludge foam, was clarified. Comparative 16S rRNA gene sequence studies indicated that the organisms formed a distinct lineage within the Corynebacterineae 16S rRNA gene tree. The taxonomic integrity of this group was underpinned by a wealth of phenotypic data, notably characteristic rudimentary right-angled branching. In addition, isolate J81T contained the following: meso-diaminopimelic acid, arabinose and galactose; N-glycolated muramic acid residues; a dihydrogenated menaquinone with eight isoprene units as the predominant isoprenologue; a fatty acid profile rich in oleic and palmitoleic acids and with relatively small proportions of myristic, stearic and tuberculostearic acids; mycolic acids with 44–52 carbons; and diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannosides as major polar lipids. Strain J81T was found to have a chemotaxonomic profile that serves to distinguish it from representatives of all of the other taxa classified as belonging to the suborder Corynebacterineae. In the light of these data, it is proposed that the two isolates be classified in a novel monospecific genus. The name proposed for this taxon is Millisia brevis gen. nov., sp. nov.; strain J81T (=DSM 44463T=NRRL B-24424T) is the type strain of Millisia brevis

Bendigoles A~C, New Steroids from Gordonia australis Acta 2299†

Bendigoles A~C are the first secondary metabolites to be isolated from a member of the actinomycete genus Gordonia. They were detected in a culture filtrate extract of Gordonia australis Acta 2299 by HPLC-diode array analysis and characterized as new steroids by mass spectrometry and NMR experiments. Bendigole C show binding affinity to the human progesterone and A~C to androgen receptor but are inactive at mineralocorticoid and estrogen receptors. In in vitro transactivation studies bendigoles A and C showed moderate and weak androgenic activities