The Effects of Chromium on Cellular Viability and Chromium Tolerant Gene Expression within Synechococcus sp. IU 625

Heavy metal contamination in the environment is always a big concern. Many microorganisms have developed metal tolerant /resistant mechanisms to survive in such environment. Cyanobacteria Synechococcus sp. IU 625 (S IU 625) formerly known as Anacystis nidulans have been used an indicator for studying many EPA targeted heavy metals such as Zn+2, Cu+2, Hg+2. This microorganism has been reported to have resistant mechanisms to mercury and zinc. In this study, in silico analysis was used to determine the pANL plasmid-mediated chromium resistant genes of Synechococcus sp. IU 625. DOOR and STRING were used to determine the operons and identity potential transcription factors. PCR primers were designed to amplify each gene within the proposed operon. Sequencing revealed high homology to S. elongatus PCC 7942 conservation among the Synechococcus genus. To monitor gene expression, S. IU 625 cultures were supplemented with increasing concentrations of chromium and isolated on hours 0, 8, 24, and 48. Samples were subject to RT-PCR and q-PCR to quantify the proposed chromium resistance operon and transcription regulators in the presences and absence of chromium. Results showed that all genes encoding the srpCDE operon are co-expressed in high concentrations of chromium. These also, a chromosomal transcription regulator showed increased co-expression with the operon. Furthermore, the pANL plasmid, in which the operon is located, increased in number as an adaptive response to chromium stress