Zarate Dani, Isenberg Ruth Y, Pavelsky Morgan, Speare Lauren, Jackson Aundre, Mandel Mark J, Septer Alecia N
Earth, Marine & Environmental Sciences Department, University of North Carolina, Chapel Hill, NC.
Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, WI.
bioRxiv. 2024 Dec 20:2024.12.19.629378. doi: 10.1101/2024.12.19.629378.
Strain-level variation among host-associated bacteria often determines host range and the extent to which colonization is beneficial, benign, or pathogenic. is a beneficial symbiont of the light organs of fish and squid with known strain-specific differences that impact host specificity, colonization efficiency, and interbacterial competition. Here, we describe how the conserved global regulator, H-NS, has a strain-specific impact on a critical colonization behavior: biofilm formation. We isolated a mutant of the fish symbiont MJ11 with a transposon insertion in the gene. This mutant formed sticky, moderately wrinkled colonies on LBS plates, a condition not known to induce biofilm in this species. A reconstructed mutant displayed the same wrinkled colony, which became smooth when was complemented , indicating the disruption is causal for biofilm formation in MJ11. Transcriptomes revealed differential expression for the biofilm locus in the mutant, relative to the parent, suggesting biofilm may in part involve SYP polysaccharide. However, enhanced biofilm in the MJ11 mutant was not sufficient to allow colonization of a non-native squid host. Finally, moving the mutation into other strains, including the squid symbionts ES114 and ES401, and seawater isolate PP3, revealed strain-specific biofilm phenotypes: ES114 and ES401 mutants displayed minimal biofilm phenotypes while PP3 mutant colonies were more wrinkled than the MJ11 mutant. These findings together define H-NS as a novel regulator of symbiotic biofilm and demonstrate key strain specificity in that role.
This work, which shows how H-NS has strain-specific impacts on biofilm in , underscores the importance of studying multiple strains, even when examining highly conserved genes and functions. Our observation that knocking out a conserved regulator can result in a wide range of biofilm phenotypes, depending on the isolate, serves as a powerful reminder that strain-level variation is common and worthy of exploration. Indeed, uncovering the mechanisms of strain-specific phenotypic differences is essential to understand drivers of niche differentiation and bacterial evolution. Thus, it is important to carefully match the number and type of strains used in a study with the research question to accurately interpret and extrapolate the results beyond a single genotype. The additional work required for multi-strain studies is often worth the investment of time and resources, as it provides a broader view of the complexity of within-species diversity in microbial systems.
宿主相关细菌之间的菌株水平差异通常决定宿主范围以及定殖有益、无害或致病的程度。 是鱼类和鱿鱼发光器官的有益共生体，具有已知的菌株特异性差异，这些差异会影响宿主特异性、定殖效率和细菌间竞争。在这里，我们描述了保守的全局调节因子H-NS如何对一种关键的定殖行为——生物膜形成产生菌株特异性影响。我们分离出了鱼类共生体MJ11的一个突变体，其转座子插入到 基因中。该突变体在LBS平板上形成粘性、中度褶皱的菌落，这种条件在该物种中并不已知会诱导生物膜形成。一个重建的 突变体表现出相同的褶皱菌落，当 被互补时菌落变得光滑，这表明 的破坏是MJ11中生物膜形成的原因。转录组显示，相对于亲本， 突变体中生物膜位点的表达存在差异，这表明生物膜可能部分涉及SYP多糖。然而，MJ11 突变体中增强的生物膜不足以使其定殖于非天然的鱿鱼宿主。最后，将 突变引入其他 菌株，包括鱿鱼共生体ES114和ES,401以及海水分离株PP3，揭示了菌株特异性的生物膜表型：ES114和ES401 突变体表现出最小的生物膜表型，而PP3 突变体菌落比MJ11 突变体更皱。这些发现共同将H-NS定义为 共生生物膜的一种新型调节因子，并证明了该作用中的关键菌株特异性。
这项工作展示了H-NS如何对 中的生物膜产生菌株特异性影响，强调了即使在研究高度保守的基因和功能时研究多个菌株的重要性。我们的观察结果表明，敲除一个保守的调节因子会导致广泛的生物膜表型，这取决于分离株，有力地提醒我们菌株水平的差异很常见且值得探索。事实上，揭示菌株特异性表型差异的机制对于理解生态位分化和细菌进化的驱动因素至关重要。因此，重要的是要仔细将研究中使用的菌株数量和类型与研究问题相匹配，以便准确解释结果并将其外推到单个基因型之外。多菌株研究所需的额外工作通常值得投入时间和资源，因为它提供了微生物系统中物种内多样性复杂性的更广泛视角。
