报告题目：Uncovering the Hidden Mechanisms of Cryptic Thermal Micro-Diversity in Cyanobacteria （蓝藻热适应多样性的隐藏机制）
报告人：David A. Hutchins（教授）
工作单位：University of Southern California （南加州大学）
报告人简介：David A. Hutchins is a Professor of Marine and Environmental Biology at the University of Southern California, where he holds the George and Louise Kawamoto Chair in Biological Sciences. He got his Ph.D. in 1994 at U.C. Santa Cruz, did a postdoc from 1994-1996 at SUNY Stony Brook and was on the faculty at U. Delaware from 1996-2007. His research uses experimental methods in the laboratory and the field to understand the consequences of global change processes for ocean biology and elemental cycling. Hutchins’ lab group has worked in marine environments ranging from the tropics to the polar seas to understand the ecological impacts of ocean acidification, warming, and deoxygenation using tools that include physiological, biochemical, biogeochemical and molecular methods. Particular areas of interest include microbial trace metal biogeochemistry, experimental evolution, marine nitrogen fixation, and harmful algal blooms. Recent work has addressed how ocean alkalinity enhancement for carbon capture may affect marine biological communities. He has published over 220 peer-reviewed papers, and is a Fellow of the American Association for the Advancement of Science (AAAS) and a Sustaining Fellow of the Association for the Sciences of Limnology and Oceanography (ASLO). In 2023, he received the ASLO John Martin award for publishing highly influential research in the marine science field.
摘要：This talk presents the results of a project that aimed to understand the hidden molecular mechanisms underlying intraspecific thermal micro-diversity within a single coastal Synechococcus population. An estuarine microbial assemblage was collected, and incubated at 18oC and 30oC for two weeks to allow thermal selection and strain sorting to occur. Clonal Synechococcus isolates were then obtained from both temperature treatments using flow cytometry, and their thermal response curves were characterized in the laboratory. Isolates from the low and high temperature incubations were morphologically identical but thermally distinct, consisting of “cool” or “warm” thermotypes, respectively, based on their significantly different thermal optimum and upper thermal limit traits. These two contrasting Synechococcus thermotypes also exhibited consistent temperature-dependent differences in photobiology. Illumina sequencing was however completely unable to distinguish between these two thermally-divergent strains, with ＞99.99% average nucleotide identity across all the isolates. Application of long read sequencing technology ultimately showed that the relevant thermal adaptation mechanisms were not genomic at all, but differences in the two thermotypes instead correlated with m-5 cytosine methylation of the genes coding for C-phycocyanin. This thermally-significant epigenomic difference would be invisible to studies based on amplicon sequencing or metagenomics, and yet such cryptic, non-genomic, intra-specific micro-diversity could play a key role in providing thermal resiliency to cyanobacteria populations growing in a warming ocean.