Duncan Tammi R, Werner-Washburne Margaret, Northup Diana E
Department of Biology, University of New Mexico, Albuquerque, New Mexico, 87131.
J Caves Karst Stud. 2021 Mar;83(1):29-43. doi: 10.4311/2019es0118.
Siderophores are microbially-produced ferric iron chelators. They are essential for microbial survival, but their presence and function for cave microorganisms have not been extensively studied. Cave environments are nutrient-limited and previous evidence suggests siderophore usage in carbonate caves. We hypothesize that siderophores are likely used as a mechanism in caves to obtain critical nutrients such as iron. Cave bacteria were collected from Long-term parent cultures (LT PC) or Short-term parent cultures (ST PC) inoculated with ferromanganese deposits (FMD) and carbonate secondary minerals from Lechuguilla and Spider caves in Carlsbad Caverns National Park (CCNP), NM. LT PC were incubated for 10-11 years to identify potential chemolithoheterotrophic cultures able to survive in nutrient-limited conditions. ST PC were incubated for 1-3 days to identify a broader diversity of cave isolates. A total of 170 LT and ST cultures,18 pure and 152 mixed, were collected and used to classify siderophore production and type and to identify siderophore producers. Siderophore production was slow to develop (>10 days) in LT cultures with a greater number of weak siderophore producers in comparison to the ST cultures that produced siderophores in <10 days, with a majority of strong siderophore producers. Overall, 64% of the total cultures were siderophore producers, which the majority preferred hydroxamate siderophores. Siderophore producers were classified into (-, -, or ), , , and phyla using 16S rRNA gene sequencing. Our study supports our hypothesis that cave bacteria have the capability to produce siderophores in the subsurface to obtain critical ferric iron.
铁载体是微生物产生的三价铁螯合剂。它们对微生物的生存至关重要，但它们在洞穴微生物中的存在和功能尚未得到广泛研究。洞穴环境营养有限，先前的证据表明碳酸盐洞穴中存在铁载体的使用情况。我们假设铁载体可能是洞穴中获取铁等关键营养物质的一种机制。从新墨西哥州卡尔斯巴德洞穴国家公园（CCNP）的勒丘吉拉洞穴和蜘蛛洞穴接种了铁锰沉积物（FMD）和碳酸盐次生矿物的长期母培养物（LT PC）或短期母培养物（ST PC）中收集洞穴细菌。LT PC培养10 - 11年，以鉴定能够在营养有限条件下存活的潜在化能异养培养物。ST PC培养1 - 3天，以鉴定更广泛的洞穴分离物多样性。总共收集了170个LT和ST培养物，其中18个是纯培养物，152个是混合培养物，用于分类铁载体的产生和类型以及鉴定铁载体产生菌。与在<10天内产生铁载体的ST培养物相比，LT培养物中铁载体的产生发展缓慢（>10天），且产生弱铁载体的数量更多，而ST培养物中大多数是强铁载体产生菌。总体而言，64%的总培养物是铁载体产生菌，其中大多数更喜欢异羟肟酸型铁载体。使用16S rRNA基因测序将铁载体产生菌分类为（-，-，或）、、、和门。我们的研究支持了我们的假设，即洞穴细菌有能力在地下产生铁载体以获取关键的三价铁。
