Assessing the Biodegradation of Vulcanised Rubber Particles by Fungi Using Genetic, Molecular and Surface Analysis.

Millions of tonnes of tyre waste are discarded annually and are considered one of the most difficult solid wastes to recycle. A sustainable alternative for the treatment of vulcanised rubber is the use of microorganisms that can biotransform polymers and aromatic compounds and then assimilate and mineralise some of the degradation products. However, vulcanised rubber materials present great resistance to biodegradation due to the presence of highly hydrophobic cross-linked structures that are provided by the additives they contain and the vulcanisation process itself. In this work, the biodegradation capabilities of 10 fungal strains cultivated in PDA and EM solid medium were studied over a period of 4 weeks. The growth of the strains, the mass loss of the vulcanised rubber particles and the surface structure were analysed after the incubation period. With the white rot fungi Trametes versicolor and Pleurotus ostreatus, biodegradation percentages of 7.5 and 6.1%, respectively, were achieved. The FTIR and SEM-EDS analyses confirmed a modification of the abundance of functional groups and elements arranged on the rubber surface, such as C, O, S, Si, and Zn, due to the biological treatment employed. The availability of genomic sequences of P. ostreatus and T. versicolor in public repositories allowed the analysis of the genetic content, genomic characteristics and specific components of both fungal species, determining some similarities between both species and their relationship with rubber biodegradation. Both fungi presented a higher number of sequences for laccases and manganese peroxidases, two extracellular enzymes responsible for many of the oxidative reactions reported in the literature. This was confirmed by measuring the laccase and peroxidase activity in cultures of T. versicolor and P. ostreatus with rubber particles, reaching between 2.8 and 3.3-times higher enzyme activity than in the absence of rubber. The integrative analysis of the results, supported by genetic and bioinformatics tools, allowed a deeper analysis of the biodegradation processes of vulcanised rubber. It is expected that this type of analysis can be used to find more efficient biotechnological solutions in the future.

DNA repair in Corynebacterium model.

Corynebacterium spp. are a group of Gram-positive bacteria that includes plant and animal pathogens, nonpathogenic soil bacteria, and saprophytic species. Our understanding of these organisms is still poor compared with that of other bacterial organisms, but new insights offered by genome sequence data and the elucidation of gene content has provided clues about the nature, genome stability, pathogenicity and virulence of these organisms. We compared 15 Corynebacterium genomes, from pathogenic and nonpathogenic species, focusing on DNA repair genes. DNA repair is a mechanism of great importance in the maintenance of the genomic stability of any organism; inefficiency of this system can promote genomic instability and lead to death. This vulnerability makes it an interesting target in the study of means to control infectious organisms. We found that nucleotide excision repair (NER) was the only pathway whose involved genes were found in all species, suggesting that DNA integrity can be primarily maintained by NER. Recombination repair (RR) is also a well conserved pathway and most RR genes exist commonly in Corynebacterium spp. Absence of recCD genes was also shared by all species, contributing to prevent genome inversions and favoring genomic stability. Mismatch repair (MMR) appeared to be missing, although some genes in this pathway, such mutT, mutY and mutL, are present. Base excision repair (BER) and direct repair pathways are not conserved pathways, since the genes are not shared by all members; however, the existence of some seems to be enough to ensure pathway activity. An interesting fact is the persistence/acquisition of some repair genes in some species, suggesting an important role in DNA maintenance and evolution. These genes can be important targets in the investigation of the role of DNA repair in the pathogenicity of Corynebacterium species and be used as targets in therapeutic intervention. Phylogenetic analysis of uvrABC NER genes showed a pattern of clusters, in which most groups remained fixed. In general, the presence or inexistence of repair genes was shared by all the species we analyzed, and the loss or acquisition of certain DNA repair genes seems to have been an ancestral event.

A description of genes of Corynebacterium pseudotuberculosis useful in diagnostics and vaccine applications.

Corynebacterium pseudotuberculosis, a Gram-positive intracellular pathogen, is the etiological agent of caseous lymphadenitis or CLA. This bacterium infects goats and sheep and causes great economic losses worldwide annually, mainly for goat producers. Despite its importance, CLA is still poorly characterized. However, with advances in the genomic field, many C. pseudotuberculosis genes have already been characterized, mainly those related to virulence such as phospholipase D. Here, we examined the use of the several available genes of C. pseudotuberculosis and reviewed their applications in vaccine construction, more efficient diagnostics for CLA, and control of this disease, among other applications.

A description of genes of Corynebacterium pseudotuberculosis useful in diagnostics and vaccine applications

Corynebacterium pseudotuberculosis, a Gram-positive intracellular pathogen, is the etiological agent of caseous lymphadenitis or CLA. This bacterium infects goats and sheep and causes great economic losses worldwide annually, mainly for goat producers. Despite its importance, CLA is still poorly characterized. However, with advances in the genomic field, many C. pseudotuberculosis genes have already been characterized, mainly those related to virulence such as phospholipase D. Here, we examined the use of the several available genes of C. pseudotuberculosis and reviewed their applications in vaccine construction, more efficient diagnostics for CLA, and control of this disease, among other applications.