Streptomyces sp. AC04842: Genomic Insights and Functional Expression of Its Latex Clearing Protein Genes (lcp1 and lcp2) When Cultivated With Natural and Vulcanized Rubber as the Sole Carbon Source.

Rubber-degrading Actinobacteria have been discovered and investigated since 1985. Only recently, through the advancement of genomic sequencing and molecular techniques, genes and pathways involved in rubber degradation are being revealed; however, the complete degradation pathway remains unknown. Streptomyces sp. AC04842 (JCM 34241) was discovered by screening at a Culture Collection Centre in Sarawak for Actinomycetes forming a clear zone on natural rubber latex agar. Streptomyces is a dominant and well-studied soil bacterium playing an important role in soil ecology including carbon recycling and biodegradation. Streptomyces sp. AC04842 draft genome revealed the presence of 2 putative latex clearing protein (lcp) genes on its chromosome and is closely related to Streptomyces cellulosae. Under the Streptomyces genus, there are a total of 64 putative lcp genes deposited in the GenBank and UniProt database. Only 1 lcp gene from Streptomyces sp. K30 has been characterized. Unlike Streptomyces sp. K30 which contained 1 lcp gene on its chromosome, Streptomyces sp. AC04842 contained 2 lcp genes on its chromosome. Streptomyces sp. AC04842 lcp1 and lcp2 amino acid sequences showed 46.13 and 69.11%, respectively, similarity to lcp sequences of Streptomyces sp. K30. Most rubber degrading strains were known to harbor only 1 lcp gene, and only recently, 2-3 lcp homologs have been reported. Several studies have shown that lcp-homolog expression increased in the presence of rubber. To study the expression of lcp1 and lcp2 genes for Streptomyces sp. AC04842, the strain was incubated in different types of rubber as the sole carbon source. In general, the lcp1 gene was highly expressed, while the lcp2 gene expression was upregulated in the presence of vulcanized rubber. Mixtures of natural and vulcanized rubber did not further increase the expression of both lcp genes compared with the presence of a specific rubber type. In this study, we paved the way to the exploration of lcp homologs and their function in degrading different types of rubber.