Mangiapia Mary, Brown Terry-René W, Chaput Dale, Haller Edward, Harmer Tara L, Hashemy Zahra, Keeley Ryan, Leonard Juliana, Mancera Paola, Nicholson David, Stevens Stanley, Wanjugi Pauline, Zabinski Tania, Pan Chongle, Scott Kathleen M
Department of Integrative Biology, University of South Florida, Tampa, Florida, USA.
Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, Florida, USA.
J Bacteriol. 2017 Mar 14;199(7). doi: 10.1128/JB.00871-16. Print 2017 Apr 1.
Many autotrophic microorganisms are likely to adapt to scarcity in dissolved inorganic carbon (DIC; CO + HCO + CO) with CO concentrating mechanisms (CCM) that actively transport DIC across the cell membrane to facilitate carbon fixation. Surprisingly, DIC transport has been well studied among cyanobacteria and microalgae only. The deep-sea vent gammaproteobacterial chemolithoautotroph has a low-DIC inducible CCM, though the mechanism for uptake is unclear, as homologs to cyanobacterial transporters are absent. To identify the components of this CCM, proteomes of cultivated under low- and high-DIC conditions were compared. Fourteen proteins, including those comprising carboxysomes, were at least 4-fold more abundant under low-DIC conditions. One of these proteins was encoded by ; strains carrying mutated copies of this gene, as well as the adjacent , required elevated DIC for growth. Strains carrying mutated copies of and overexpressed carboxysomes and had diminished ability to accumulate intracellular DIC. Based on reverse transcription (RT)-PCR, and were cotranscribed and upregulated under low-DIC conditions. The -encoded protein was predicted to have 13 transmembrane helices. Given the mutant phenotypes described above, and may encode a two-subunit DIC transporter that belongs to a previously undescribed transporter family, though it is widespread among autotrophs from multiple phyla. DIC uptake and fixation by autotrophs are the primary input of inorganic carbon into the biosphere. The mechanism for dissolved inorganic carbon uptake has been characterized only for cyanobacteria despite the importance of DIC uptake by autotrophic microorganisms from many phyla among the and In this work, proteins necessary for dissolved inorganic carbon utilization in the deep-sea vent chemolithoautotroph were identified, and two of these may be able to form a novel transporter. Homologs of these proteins are present in 14 phyla in and also in one phylum of , the Many organisms carrying these homologs are autotrophs, suggesting a role in facilitating dissolved inorganic carbon uptake and fixation well beyond the genus .
许多自养微生物可能通过二氧化碳浓缩机制（CCM）来适应溶解无机碳（DIC；CO₂ + HCO₃⁻ + CO₃²⁻）的稀缺，该机制可主动将DIC转运穿过细胞膜以促进碳固定。令人惊讶的是，DIC转运仅在蓝细菌和微藻中得到了充分研究。深海热液γ-变形菌化能无机自养菌具有低DIC诱导型CCM，尽管其摄取机制尚不清楚，因为不存在与蓝细菌转运蛋白同源的蛋白。为了鉴定这种CCM的组成成分，比较了在低DIC和高DIC条件下培养的该菌的蛋白质组。14种蛋白质，包括构成羧酶体的蛋白质，在低DIC条件下的丰度至少高4倍。其中一种蛋白质由[基因名称]编码；携带该基因以及相邻基因的突变拷贝的菌株，生长需要更高的DIC。携带[基因名称]和[另一基因名称]突变拷贝的菌株羧酶体过度表达，积累细胞内DIC的能力减弱。基于逆转录（RT）-PCR，[基因名称]和[另一基因名称]共转录且在低DIC条件下上调。预测由[基因名称]编码的蛋白质有13个跨膜螺旋。鉴于上述突变体表型，[基因名称]和[另一基因名称]可能编码一种属于先前未描述的转运蛋白家族的双亚基DIC转运蛋白，尽管它在多个门的自养生物中广泛存在。自养生物对DIC的摄取和固定是无机碳进入生物圈的主要输入。尽管在[具体分类群]和[另一具体分类群]中许多门的自养微生物对DIC的摄取很重要，但溶解无机碳摄取机制仅在蓝细菌中得到了表征。在这项工作中，鉴定了深海热液化能无机自养菌中溶解无机碳利用所需的蛋白质，其中两种可能能够形成一种新型转运蛋白。这些蛋白质的同源物存在于[具体分类群]的14个门以及[另一具体分类群]的一个门中，即[该门名称]。许多携带这些同源物的生物是自养生物，这表明它们在促进溶解无机碳摄取和固定方面的作用远远超出了[属名]属。
