Shaffer Jacob M C, Giddings Lesley-Ann, Samples Robert M, Mikucki Jill A
Department of Microbiology, University of Tennessee, Knoxville, TN, United States.
Department of Chemistry, Smith College, Northampton, MA, United States.
Front Microbiol. 2023 May 12;14:1156033. doi: 10.3389/fmicb.2023.1156033. eCollection 2023.
The McMurdo Dry Valleys of Antarctica experience a range of selective pressures, including extreme seasonal variation in temperature, water and nutrient availability, and UV radiation. Microbial mats in this ecosystem harbor dense concentrations of biomass in an otherwise desolate environment. Microbial inhabitants must mitigate these selective pressures specialized enzymes, changes to the cellular envelope, and the production of secondary metabolites, such as pigments and osmoprotectants. Here, we describe the isolation and characterization of a Gram-negative, rod-shaped, motile, red-pigmented bacterium, strain DJPM01, from a microbial mat within the Don Juan Pond Basin of Wright Valley. Analysis of strain DJMP01's genome indicates it can be classified as a member of the species. The genome contains several genes associated with cold and salt tolerance, including multiple RNA helicases, protein chaperones, and cation/proton antiporters. In addition, we identified 17 putative secondary metabolite gene clusters, including a number of nonribosomal peptides and ribosomally synthesized and post-translationally modified peptides (RiPPs), among others, and the biosynthesis pathway for the antimicrobial pigment prodigiosin. When cultivated on complex agar, multiple prodiginines, including the antibiotic prodigiosin, 2-methyl-3-propyl-prodiginine, 2-methyl-3-butyl-prodiginine, 2-methyl-3-heptyl-prodiginine, and cycloprodigiosin, were detected by LC-MS. Genome analyses of sequenced members of the genus indicates prodigiosin production is unique to Antarctic strains. UV-A radiation, an ecological stressor in the Antarctic, was found to significantly decrease the abundance of prodiginines produced by strain DJPM01. Genomic and phenotypic evidence indicates strain DJPM01 can respond to the ecological conditions of the DJP microbial mat, with prodiginines produced under a range of conditions, including extreme UV radiation.
南极洲的麦克默多干谷面临一系列选择压力，包括温度、水和养分可利用性以及紫外线辐射的极端季节性变化。在这个生态系统中，微生物垫在原本荒凉的环境中蕴藏着密集的生物量。微生物居民必须通过特殊的酶、细胞包膜的变化以及次生代谢产物（如色素和渗透保护剂）的产生来减轻这些选择压力。在这里，我们描述了从赖特谷唐璜池塘盆地的一个微生物垫中分离和鉴定出的一株革兰氏阴性、杆状、有鞭毛、红色色素细菌，菌株DJPM01。对菌株DJMP01基因组的分析表明，它可被归类为该物种的一个成员。该基因组包含几个与耐寒和耐盐相关的基因，包括多个RNA解旋酶、蛋白质伴侣和阳离子/质子反向转运蛋白。此外，我们鉴定出17个假定的次生代谢产物基因簇，包括一些非核糖体肽和核糖体合成及翻译后修饰肽（RiPPs）等，以及抗菌色素灵菌红素的生物合成途径。当在复杂琼脂上培养时，通过液相色谱 - 质谱法检测到多种灵菌红素，包括抗生素灵菌红素、2 - 甲基 - 3 - 丙基 - 灵菌红素、2 - 甲基 - 3 - 丁基 - 灵菌红素、2 - 甲基 - 3 - 庚基 - 灵菌红素和环灵菌红素。对该属已测序成员的基因组分析表明，灵菌红素的产生是南极菌株所特有的。紫外线A辐射是南极的一种生态应激源，被发现会显著降低菌株DJPM01产生的灵菌红素的丰度。基因组和表型证据表明，菌株DJPM01能够响应DJP微生物垫的生态条件，在一系列条件下产生灵菌红素，包括极端紫外线辐射。
