{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T19:08:38Z","timestamp":1789153718969,"version":"build-2803163510"},"posted":{"date-parts":[[2026,9,8]]},"group-title":"Microbiology","reference-count":37,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T00:00:00Z","timestamp":1788825600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,9,8]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>\n                  Carbonic anhydrase (E.C. 4.2.1.1) is an enzyme that catalyzes the reversible hydration of CO\n                  <jats:sub>2<\/jats:sub>\n                  to carbonic acid (H\n                  <jats:sub>2<\/jats:sub>\n                  CO\n                  <jats:sub>3<\/jats:sub>\n                  ), which dissociates to bicarbonate (HCO\n                  <jats:sub>3<\/jats:sub>\n                  <jats:sup>\u2212<\/jats:sup>\n                  ) at intracellular pH. Copious amounts of CO\n                  <jats:sub>2<\/jats:sub>\n                  are produced by catabolism, although much of this is lost by diffusion from the cell. In\n                  <jats:italic>Bacillus subtilis<\/jats:italic>\n                  , anabolic processes rely largely on bicarbonate as a substrate rather than CO\n                  <jats:sub>2<\/jats:sub>\n                  . While CO\n                  <jats:sub>2<\/jats:sub>\n                  reacts spontaneously with water to yield bicarbonate, the rate of this reaction is too slow to keep up with cell requirements.\n                  <jats:italic>B. subtilis<\/jats:italic>\n                  encodes three putative \u03b2-class carbonic anhydrases, here renamed\n                  <jats:italic>canA<\/jats:italic>\n                  (\n                  <jats:italic>yvdA)<\/jats:italic>\n                  ,\n                  <jats:italic>canB<\/jats:italic>\n                  (\n                  <jats:italic>ytiB<\/jats:italic>\n                  ), and\n                  <jats:italic>canC<\/jats:italic>\n                  (\n                  <jats:italic>ybcF)<\/jats:italic>\n                  . The\n                  <jats:italic>canC<\/jats:italic>\n                  gene is encoded in an operon with\n                  <jats:italic>ndhF<\/jats:italic>\n                  -\n                  <jats:italic>mpsB<\/jats:italic>\n                  (\n                  <jats:italic>ybcC)<\/jats:italic>\n                  , which encodes a candidate MpsAB-type bicarbonate transporter. Here we demonstrate that a strain lacking\n                  <jats:italic>canA, canB, canC,<\/jats:italic>\n                  and\n                  <jats:italic>mpsB<\/jats:italic>\n                  (\u03944) has a severe growth defect at atmospheric CO\n                  <jats:sub>2<\/jats:sub>\n                  . This defect can be overcome by growing cells with supplemental CO\n                  <jats:sub>2<\/jats:sub>\n                  or by plating at high cell density. We isolated suppressors of \u03944 and identified mutations in\n                  <jats:italic>resD<\/jats:italic>\n                  that suppress the requirement for supplemental CO\n                  <jats:sub>2<\/jats:sub>\n                  to support growth. ResD functions as a global regulator of genes important for both aerobic and anaerobic respiration. We demonstrate that a\n                  <jats:italic>resD<\/jats:italic>\n                  null mutation results in metabolic changes that lead to an increased generation of CO\n                  <jats:sub>2<\/jats:sub>\n                  . We infer that this results in an increase in spontaneous bicarbonate formation that is sufficient to support cell growth. We conclude that the requirement for bicarbonate concentrating mechanisms may be bypassed under conditions that increase endogenous CO\n                  <jats:sub>2<\/jats:sub>\n                  generation.\n                <\/jats:p>\n                <jats:sec>\n                  <jats:title>Importance<\/jats:title>\n                  <jats:p>\n                    Carbonic anhydrase (CA) catalyzes the reversible hydration of CO\n                    <jats:sub>2<\/jats:sub>\n                    to bicarbonate. This enzyme is found in all domains of life and has evolved multiple times. In heterotrophic organisms, CA is important for concentrating bicarbonate for anabolic reactions such as fatty acid, amino acid, and menaquinone synthesis. Bicarbonate can also be directly imported by dedicated transporters. Free-living bacteria are often unable to grow in the absence of a bicarbonate concentrating mechanism, and CAs and bicarbonate transporters are also important in pathogenesis. Thus, understanding how cells obtain bicarbonate may lead to the development of novel antibiotics and highlight new therapeutic targets.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.64898\/2026.09.08.750065","type":"posted-content","created":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T04:20:18Z","timestamp":1788927618000},"source":"Crossref","is-referenced-by-count":0,"title":["Physiological Roles of Carbonic Anhydrases and an MpsAB-like Bicarbonate Transporter in\n                  <i>Bacillus subtilis<\/i>"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0009-0000-9411-599X","authenticated-orcid":false,"given":"Grayson","family":"Barnes","sequence":"first","affiliation":[{"name":"Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3832-3249","authenticated-orcid":false,"given":"John D.","family":"Helmann","sequence":"additional","affiliation":[{"name":"Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"54368","reference":[{"key":"2026091111402548000_2026.09.08.750065v1.1","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1113\/jphysiol.1933.sp003078","article-title":"The state of carbon dioxide in blood","volume":"80","year":"1933","journal-title":"J Physiol"},{"key":"2026091111402548000_2026.09.08.750065v1.2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.96.26.15184"},{"key":"2026091111402548000_2026.09.08.750065v1.3","doi-asserted-by":"crossref","first-page":"ycag054","DOI":"10.1093\/ismeco\/ycag054","article-title":"Genomic and metagenomic survey of microbial carbonic anhydrase genes reveals novel clades, high diversity, and biome specificity","volume":"6","year":"2026","journal-title":"ISME Commun"},{"key":"2026091111402548000_2026.09.08.750065v1.4","doi-asserted-by":"publisher","DOI":"10.1152\/physrev.2000.80.2.681"},{"key":"2026091111402548000_2026.09.08.750065v1.5","doi-asserted-by":"publisher","DOI":"10.1023\/A:1025821717773"},{"key":"2026091111402548000_2026.09.08.750065v1.6","doi-asserted-by":"publisher","DOI":"10.1128\/JB.185.21.6415-6424.2003"},{"key":"2026091111402548000_2026.09.08.750065v1.7","doi-asserted-by":"crossref","first-page":"3627","DOI":"10.1038\/s41467-019-11547-5","article-title":"MpsAB is important for Staphylococcus aureus virulence and growth at atmospheric CO(2) levels","volume":"10","year":"2019","journal-title":"Nat Commun"},{"key":"2026091111402548000_2026.09.08.750065v1.8","doi-asserted-by":"crossref","first-page":"e0097021","DOI":"10.1128\/Spectrum.00970-21","article-title":"Staphylococcus aureus Genomes Harbor Only MpsAB-Like Bicarbonate Transporter but Not Carbonic Anhydrase as Dissolved Inorganic Carbon Supply System","volume":"9","year":"2021","journal-title":"Microbiol Spectr"},{"key":"2026091111402548000_2026.09.08.750065v1.9","doi-asserted-by":"publisher","DOI":"10.1007\/s00239-008-9191-4"},{"key":"2026091111402548000_2026.09.08.750065v1.10","doi-asserted-by":"publisher","DOI":"10.1186\/s13567-018-0583-1"},{"key":"2026091111402548000_2026.09.08.750065v1.11","doi-asserted-by":"crossref","unstructured":"Varesio LM , Willett JW , Fiebig A , Crosson S . 2019. 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