Mechanical and cell-to-cell adhesive properties of aggregated Methanosarcina

Probing the Surface Layer Modulation on Archaeal Mechanics and Adhesion at the Single-Cell Level

Addressing the challenge of understanding how cellular interfaces dictate the mechanical resilience and adhesion of archaeal cells, this study demonstrates the role of the surface layer (S-layer) in methanogenic archaea. Using a combination of atomic force microscopy and single-cell force spectroscopy, we quantified the impact of S-layer disruption on cell morphology, mechanical properties, and adhesion capabilities. We demonstrate that the S-layer is crucial for maintaining cell morphology, where its removal induces significant cellular enlargement and deformation. Mechanical stability of the cell surface is substantially compromised upon S-layer disruption, as evidenced by decreased Young's modulus values. Adhesion experiments revealed that the S-layer primarily facilitates hydrophobic interactions, which are significantly reduced after its removal, affecting both cell-cell and cell-bubble interactions. Our findings illuminate the S-layer's fundamental role in methanogen architecture and provide a chemical understanding of archaeal cell surfaces, with implications for enhancing methane production in biotechnological applications.

The Compressed Vocabulary of Microbial Life

Communication is an undisputed central activity of life that requires an evolving molecular language. It conveys meaning through messages and vocabularies. Here, I explore the existence of a growing vocabulary in the molecules and molecular functions of the microbial world. There are clear correspondences between the lexicon, syntax, semantics, and pragmatics of language organization and the module, structure, function, and fitness paradigms of molecular biology. These correspondences are constrained by universal laws and engineering principles. Macromolecular structure, for example, follows quantitative linguistic patterns arising from statistical laws that are likely universal, including the Zipf's law, a special case of the scale-free distribution, the Heaps' law describing sublinear growth typical of economies of scales, and the Menzerath-Altmann's law, which imposes size-dependent patterns of decreasing returns. Trade-off solutions between principles of economy, flexibility, and robustness define a "triangle of persistence" describing the impact of the environment on a biological system. The pragmatic landscape of the triangle interfaces with the syntax and semantics of molecular languages, which together with comparative and evolutionary genomic data can explain global patterns of diversification of cellular life. The vocabularies of proteins (proteomes) and functions (functionomes) revealed a significant universal lexical core supporting a universal common ancestor, an ancestral evolutionary link between Bacteria and Eukarya, and distinct reductive evolutionary strategies of language compression in Archaea and Bacteria. A "causal" word cloud strategy inspired by the dependency grammar paradigm used in catenae unfolded the evolution of lexical units associated with Gene Ontology terms at different levels of ontological abstraction. While Archaea holds the smallest, oldest, and most homogeneous vocabulary of all superkingdoms, Bacteria heterogeneously apportions a more complex vocabulary, and Eukarya pushes functional innovation through mechanisms of flexibility and robustness.

Wastewater biofilm formation on self-assembled monolayer surfaces using elastomeric flow cells

In anaerobic wastewater treatment, microbial biofilm is beneficial for efficient substrate utilization and for preventing the wash-out of key microorganisms. By providing solid supports, biofilm formation can be accelerated due to the early initial adhesion of residing microbes. Alteration in surface properties is therefore one such approach that helps us understand microbial interfacial interaction. Here, self-assembled monolayers of alkanethiols with carboxyl (-COOH), hydroxyl (-OH), and amine (-NH₂) terminal moieties on gold (Au) substrates were employed to study the initial adhesion of wastewater microbes. An elastomeric flow cell was also utilized to simulate the environment of wastewater bioreactor. Results from fluorescence in situ hybridization (FISH) portrayed more enhanced microbial adhesion after 2 h on -NH₂ functional group with the calculated surface coverage of 12.8 ± 2.4% as compared to 7.7 ± 1.6% on -COOH, 11.0 ± 2.0% on -OH, and 1.2% on unmodified Au surfaces. This might be because of concomitant electrostatic attraction between negatively-charged bacteria and positively-charged (-NH₃⁺) functional groups. Nevertheless, the average surface coverage by individual biofilm clusters was 28.0 ± 5.0 μm² and 32.0 ± 9.0 μm² on -NH₂ and -OH surfaces, respectively, while -COOH surfaces resulted in higher value (60.0 ± 5.0 μm²) and no significant cluster formation was observed on Au surfaces. Accordingly, the average inter-cluster distance observed on -NH₂ surfaces was relatively smaller (3.0 ± 0.6 μm) as compared to that on other surfaces. Overall, these data suggest favorable initial biofilm growth on more hydrophilic and positively-charged surfaces. Furthermore, the analysis of the mean fluorescence intensity revealed preferred initial adhesion of key microbes (archaea) on -OH and -NH₂ surfaces. Indeed, results obtained from this study would be beneficial in designing selective biointerfaces for certain biofilm carriers in a typical wastewater bioreactor. Importantly, our elastomeric flow cell integrated with SAM-modified surfaces demonstrated an ideal platform for high-throughput investigation of wastewater biofilm under controlled environments.