Draft Genome Sequence of Rhodococcus rhodochrous Strain G38GP, Isolated from the Madagascar Hissing Cockroach

Rhodococcus rhodochrous is a bacterial species with applications in biocatalysis and bioremediation. Here, we report the draft genome sequence of strain G38GP, isolated from the gut of the cockroach Gromphadorhina portentosa . The genome consists of 76 contigs, with a total length of 6,256,198 bp and a GC content of 67.82%.

Bacterial Transformation of Aromatic Monomers in Softwood Black Liquor

The valorization of lignin, a major component of plant-derived biomass, is essential to sustainable biorefining. We identified the major monoaromatic compounds present in black liquor, a lignin-rich stream generated in the kraft pulping process, and investigated their bacterial transformation. Among tested solvents, acetone extracted the greatest amount of monoaromatic compounds from softwood black liquor, with guaiacol, vanillin, and acetovanillone, in an approximately 4:3:2 ratio, constituting ~90% of the total extracted monoaromatic content. 4-Ethanol guaiacol, vanillate, and 4-propanol guaiacol were also present. Bacterial strains that grew on minimal media supplemented with the BL extracts at 1mM total aromatic compounds included Pseudomonas putida KT2442, Sphingobium sp. SYK-6, and Rhodococcus rhodochrous EP4. By contrast, the extracts inhibited the growth of Rhodococcus jostii RHA1 and Rhodococcus opacus PD630, strains extensively studied for lignin valorization. Of the strains that grew on the extracts, only R. rhodochrous GD01 and GD02, isolated for their ability to grow on acetovanillone, depleted the major extracted monoaromatics. Genomic analyses revealed that EP4, GD01, and GD02 share an average nucleotide identity (ANI) of 98% and that GD01 and GD02 harbor a predicted three-component carboxylase not present in EP4. A representative carboxylase gene was upregulated ~100-fold during growth of GD02 on a mixture of the BL monoaromatics, consistent with the involvement of the enzyme in acetovanillone catabolism. More generally, quantitative RT-PCR indicated that GD02 catabolizes the BL compounds in a convergent manner via the β-ketoadipate pathway. Overall, these studies help define the catabolic capabilities of potential biocatalytic strains, describe new isolates able to catabolize the major monoaromatic components of BL, including acetovanillone, and facilitate the design of biocatalysts to valorize under-utilized components of industrial lignin streams.

Viability and phenotypic heterogeneity of Rhodococcus Rhodochrous CNMN-AC-05 in the presence of fullerene C60

Introduction. In recent years, due to wide applications of nanotechnologies in various fields, the safety of nanomaterials has become a pressing issue. Fullerene C60 is not an exception. Research on the activity of microorganisms and their interaction with nanoparticles is of major importance, both for microorganisms and for the ecosystem as a whole. Material and methods. Fullerene C60 powder was purchased from Sigma-Aldrich. The object of study was R. rhodochrous CNMN-Ac-05 strain. The number of viable bacterial cells was estimated by colony-forming units (CFU). The morphological features of the rhodococci colonies have been described according to the usual microbiological method. Results. It was established that fullerene C60 in concentrations of 1-25 mg/L fullerene C60 stimulated the growth of R. rhodochrous by 2.4-2.8 times. As the concentration of fullerene C60 increased up to 50-100 mg/L, the multiplication and growth of rhodococci decreased by 29.5% and 38% respectively. In the presence of 1-10 mg/L fullerene C60 the rhodococci population remained homogeneous, being composed of 100% S type colonies. The increase of fullerene C60 concentration led both to the decrease in the CFU number and to the appearance of R type colonies, up to 1.3% of population. Conclusions. Fullerene C60 in concentrations 1-100 mg/L had no obvious toxic effect on the rhodococci strain. The optimum concentration is 10 mg/L. The concentrations higher than 25 mg/L led to the dissociation of rhodococcal population and diminution in the CFU counts, but not to the total inhibition.

Dissociation of Rhodococcus rhodochrous Population after the Whole Cells Immobilization

Six agricultural organic wastes and three inorganic matrices were selected for rhodococci whole cells immobilization. The degree of immobilization of rhodococci cells varied from 6.20% to 34.30% on organic matrices. A high level of Rhodococcus rhodochrous CNMN-Ac-05 cells immobilization was demonstrated on inorganic matrices, it was from 69.25% to 97.30%. After the contact with support the strain dissociated, forming, in addition to original S type, rough (R) and altercolour smooth (S) types. Immobilization of rhodococci cells on organic supports led to the appearance of phenotypic heterogeneity from 0.34% to 3.26%. On inorganic matrices the variability of rhodococci was 0.88-1.05%.

Comparative Fatty Acid Profiling of Klebsiella pneumoniae and Rhodococcus rhodochrous Isolated from Spoilt Paints by Gas Chromatography

The use of fatty acids to study the differences in un-related microbes is limited. This study analyzes the fatty acids produced by two unrelated microorganisms: Klebsiella pneumoniae (Gram-negative, aerobic, non-endospore forming, usually encapsulated rod-shaped bacteria of the family Enterobacteriaceae) and Rhodococcus rhodochrous (metabolically versatile, non-spore-forming, non-motile actinomycete) isolated from spoilt paints. Fatty acids produced by the organisms were analyzed using an efficient MIDI-Sherlock gas chromatography method . K. pneumoniae was characterized by a high content of straight chain, branched chain, hydroxyl and cyclo-fatty acids made up of C12: 0, C13:0, C14:0 iso, C14:0, C15:0 iso, C15:0 anteiso, C15:1 ω 8c, C15:0, C16:0 iso, C16:1w5c, C16:0, C15:03OH, C17:1 ω 8c, C17:0 cyclo, C17:0, C18:1 ω5c and C18:0. R. rhodochrous was dominated by straight chain, monounsaturated and 10-methyl fatty acids. The inability to synthesize branched, cyclo- and hydroxyl- fatty acids, was observed in R. rhodochrous which composed mainly of C14: 0, C15: 1 ω 5c, C15:0, C16:1 ω 9c, C16:0, C17:1 ω 8c, C17:0, C17:0 10-methyl, C18: 1 ω 9c, C18.0, 10 methyl-C18:0 TBSA, C20:1 ω 9c, and C20:0. Descriptive statistics reveal a mean of 2.53, 15.10 and 15.15 for retention time (RT), equivalent chain length (ECL) and Peak name, respectively. Possible implications of the variations in fatty acid distribution may include differences in their abilities to produce various secondary metabolites and potentials to degrade a variety of xenobiotics. Keywords: Fatty acids, paints, Rhodococcus rhodochrous, Klebsiella pneumoniae

The effect of Rhodococcus rhodochrous supplementation on black soldier fly (Diptera: Stratiomyidae) development, nutrition, and waste conversion

Black soldier fly larvae are mass produced globally for use as livestock, poultry, and aquaculture feed. Efforts are continuously seeking processes optimising larval rate of growth, size, and waste conversion as a means to lower cost and increase output. Manipulating microbes in the larval substrate (i.e. fermentation or supplementation) has been demonstrated as a potential solution. However, identifying appropriate microbes for use in this process has been limited. The objective of this study was to determine whether supplementing black soldier fly larvae with the oleaginous microbe Rhodococcus rhodochrous would result in accelerated larval development, increased final larval body size, and increased conversion efficiency. Larvae fed a sterile, or non-sterile, diet treated with R. rhodochrous grew 3× faster than the control by the third day and were approximately 2× larger than the control by the conclusion of the experiment. Conversion rate was 2× greater for the treatments indicating less feed would be needed to achieve maximum weight gain. Protein composition of resulting larvae fed diet supplemented with R. rhodochrous, was significantly different than the control not receiving the microbial infusion. Larvae provided the microbe had 4.20 and 2.79% greater fatty acid composition and short-chained fatty acids, respectively, but lower monounsaturated fatty acids (1.60%) and polyunsaturated fatty acids (2.4%). Furthermore, larvae provided R. rhodochrous produced significantly more proteins related to energy production and storage, as well as muscle development and contraction, while those sans microbe, produced proteins related to stress responses (e.g. heat shock proteins). While, this study yielded positive results for the inclusion of R. rhodochrous as part of the black soldier fly larval diet, additional research is needed to optimise the dose at an industrial scale.