Predicting Optimal Growth Rate of Marine Bacteria with Genetic Signatures of Cold Adaptation

The majority of the world’s ocean volume is found at temperatures below five degrees Celsius, and marine microorganisms have adapted to these conditions by various evolutionary pathways. Many of the psychrophilic organisms that thrive in cold temperatures (-20℃ to 10℃) are bacteria that could be at risk with globally warming oceans, making it increasingly important to investigate the underlying mechanisms of these adaptation to extreme conditions. Many of these crucial psychrophilic bacteria are not yet able to be cultured in the lab due to unknown growth requirements, making it impossible to measure key phenotypic characteristics such as optimal growth temperature. However, high throughput DNA sequencing of environmental communities or “metagenomics” can provide insight into the phenotypes like growth temperature in an environmental context. To achieve this, we propose to use metagenomics data of genus Colwellia with known optimal growth temperatures to create a model predicting this phenotype, thus helping to lay the groundwork in understanding the origin, adaptation, and relationship between the types of adaptation genes. A total of 44 Colwellia samples will be analyzed for their cold-adaptation sequences that determine, among other traits, membrane fluidity, amino acid substitution that affect the flexibility of proteins, hydrophobicity of the side chain, etc... Finally, cold-adaptation scores will be created by using the process described by Goordial et al. (2015), where scores are developed by matching gene sequences for proteins in the samples with those found online, making it possible to evaluate temperature adaptation based on a range of amino acid indices. We will then use multivariate phylogenetic models to predict optimal growth temperature of uncultured microorganisms in marine metagenomes. These models may then be incorporated into forecasts of microbial production in the warmer waters expected in the future around Alaska.