|TABATABAI, BEHNAM - Morgan State University|
|ARUMANAYAGAM, ANITHACHRISTY - Houston Methodist Research Institute|
|ENITAN, OLUWATOMISIN - Morgan State University|
|Natarajan, Savithiry - Savi|
|SITTHER, VIJI - Morgan State University|
Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2016
Publication Date: 11/14/2016
Citation: Tabatabai, B., Arumanayagam, A.S., Enitan, O., Natarajan, S.S., Sitther, V. 2016. Identification of a halotolerant mutant via in vitro mutagenesis in the cyanobacterium Fremyella diplosiphon. Current Microbiology. 74:77-83.
Interpretive Summary: Freshwater photosynthetic organisms like algae and cyanobacteria, which can be used to produce biofuels, are threatened by increasing environmental salinity. Elevated salinity leads to ion imbalance and hyperosmotic stress in these organisms. Therefore, enhancing salinity tolerance (halotolerance) in these organisms is important. In this research, we developed a mutant cyanobacterial species, Fremyella diplosiphon that expresses more salt tolerance-linked genes and proteins. These proteins allow the cyanobacterium to survive in water with high concentrations of salt. Development of salinity tolerant strains will pave the way for their growth in brackish fresh waters or in naturally saline, but more abundant marine waters. This information will be useful for scientists at government agencies, universities or private industries wanting to develop cyanobacteria for biofuel production in salty water. It is also possible that plant breeders can use these scientific data to understand or enhance salt tolerance in crops such as soybeans, maize, or tomatoes that grow poorly in soils with high salt concentrations.
Technical Abstract: Energy metabolism and photosynthetic pigment accumulation are affected by salt stress in cyanobacteria leading to cessation of growth. The effect of salinity on the fresh water cyanobacteria, Fremyella diplosiphon was investigated and mutagenesis-based efforts were undertaken to enhance salt tolerance. Salinity at a concentration of 10 g L-1 sodium chloride (NaCl) inhibited growth of wild-type F. diplosiphon under red, green, and white light. Mutagenesis of F. diplosiphon resulted in a mutant, Fd33-M25, that could survive in media with up to 20 g/L NaCl with no significant reduction in phycobiliproteins (phycocyanin, phycoerythrin, and allophycocyanin) or chlorophyll a. Gene expression measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) revealed a three-fold increase in TRAP transporter solute receptor transcript in the mutant compared to wild-type F. diplosiphon. SDS-PAGE revealed an up-regulation of the protein in the mutant. Our discovery of a TRAP transporter system in F. diplosiphon and its possible role in salinity responses enables the growth of F. diplosiphon in brackish waters, which enhances its potential for biotechnological applications.