Investigating Membrane Alterations as a Mechanism of Acid Tolerance in Cariogenic Bacteria

龋齿是全球最常见的慢性传染病，是由牙齿表面形成的产酸细菌生物膜引起的，这些生物膜会使保护性的牙釉质屏障脱矿并破坏。虽然氟化物治疗的效果（预防龋齿的当代标准）有充分的文献记载，但目前该疾病的流行情况清楚地表明，在许多情况下，仅靠氟化物不足以预防龋齿。因此，增加对疾病发病机制的了解和探索新的预防策略是值得关注的目标。无论涉及的微生物类群如何，细菌的耐酸性是龋齿发病中不可或缺的因素。已知的龋齿病原体变形链球菌（Streptococcus mutans）在其质膜中增加不饱和脂肪酸（UFAs）的比例，以应对环境酸化——这是耐酸和毒力所必需的适应。初步数据表明，其他几种革兰氏阳性口腔分类群，包括与龋齿相关的种，干酪乳杆菌，以类似的方式修改其膜以响应环境酸化。这项建议解决了这些意见提出的一些目前尚未解决的问题。拟议研究的目的1和2将确定整个口腔微生物组对酸应激反应的范围

Dental caries is the most common chronic infectious disease globally and is caused by the formation of acid-producing bacterial biofilms on the tooth surface, which demineralize and destroy the protective underlying enamel barrier. Although the efficacy of fluoride treatments (the contemporary standard in caries prevention) is well-documented, the current prevalence of the disease clearly illustrates that fluoride alone is insufficient to prevent caries in many situations. Therefore, increased understanding of disease pathogenesis and exploration of novel preventative strategies are objectives worthy of attention. Regardless of the microbial taxa involved, bacterial acid-tolerance is an indispensable factor in caries pathogenesis. The known caries pathogen Streptococcus mutans increases the proportion of unsaturated fatty acids (UFAs) in its plasma membrane in response to environmental acidification—an adaptation required for acid-tolerance and virulence. Preliminary data indicates that several other Gram-positive oral taxa, including the caries-associated species, Lactobacillus casei, modify their membranes in a similar manner in response to environmental acidification. This proposal addresses a number of currently unanswered questions raised by these observations. Aims 1 and 2 of the proposed research will determine the scope of this response to acid stress across the oral microbiome, in single taxa or in a community setting. Aim 3 of this proposal will elucidate how these UFAs are protective against acid-mediated damage. These aims will be accomplished using bioinformatics tools, basic molecular microbiology, an ecologically-relevant and complex in vitro oral biofilm model, and mass spectrometry/lipidomics. Successful completion of the proposed research will answer pertinent questions regarding caries pathogenesis in a multispecies setting and is likely to open the door to investigation of novel anti-caries therapeutics which, while targeting acidophiles, function regardless of the presence and abundance of S. mutans. The candidate, Dr. Jonathon Baker, has a longstanding interest in the microbiology of dental caries. Upon completion of the K99 (mentored) phase of this award, his goal is to become an independent PI at a leading research university, where he plans to continue research on the modifications that bacteria make to their membranes to combat environmental stresses, while leveraging acquired data to develop novel therapeutics. A funded K99/R00 proposal will allow Dr. Baker to develop skills necessary to both complete the proposed research (training in mass spectrometry/lipidomics) and subsequently become an independent research scientist (training in didactic lecturing, mentoring, and grantsmanship). Dr. Baker’s mentors and environment: Drs. Karen Nelson (J. Craig Venter Institute), Anna Edlund (J. Craig Venter Institute/UC San Diego), Pieter Dorrestein (UC San Diego), Victor Nizet (UC San Diego) and Robert Quivey, Jr. (University of Rochester School of Medicine and Dentistry) have been carefully selected to provide high-quality, diverse scientific and collegial support, as well as state-of-the-art facilities, to ensure successful completion of this research program and the proposed career development goals.