Abstract
Gram-negative bacteria experiencing marine habitats are constantly exposed to stressful conditions dictating their survival and proliferation. In response to these selective pressures, marine microorganisms adapt their membrane system to ensure protection and dynamicity in order to face the highly mutable sea environments. As an integral part of the Gram-negative outer membrane, structural modifications are commonly observed in the lipopolysaccharide (LPS) molecule; these mainly involve its glycolipid portion, i.e., the lipid A, mostly with regard to fatty acid content, to counterbalance the alterations caused by chemical and physical agents. As a consequence, unusual structural chemical features are frequently encountered in the lipid A of marine bacteria. By a combination of data attained from chemical, MALDI-TOF mass spectrometry (MS), and MS/MS analyses, here, we describe the structural characterization of the lipid A isolated from two marine bacteria of the Echinicola genus, i.e., E. pacifica KMM 6172T and E. vietnamensis KMM 6221T. This study showed for both strains a complex blend of mono-phosphorylated tri- and tetra-acylated lipid A species carrying an additional sugar moiety, a d-galacturonic acid, on the glucosamine backbone. The unusual chemical structures are reflected in a molecule that only scantly activates the immune response upon its binding to the LPS innate immunity receptor, the TLR4-MD-2 complex. Strikingly, both LPS potently inhibited the toxic effects of proinflammatory Salmonella LPS on human TLR4/MD-2.
Highlights
Marine environments host remarkably high and diverse microbial populations considered as the oldest life on the planet
LPS from bacterial cells of E. pacifica KMM 6172T and E. vietnamensis KMM 6221T were isolated through the hot phenol/water method [16]
Since some LPS isolated from marine bacteria have shown a fascinating potential as inhibitors of the proinflammatory action of LPS from pathogenic bacteria, we investigated the capability of LPS from the two Echinicola strains to interfere with the TLR4mediated signaling triggered by S. typhimurium LPS
Summary
Marine environments host remarkably high and diverse microbial populations considered as the oldest life on the planet. Unveiling the molecular mechanisms at the basis of the microbial adaptation to this complex environment is a prolific and intriguing area of research, with marine bacteria attracting most researchers’ attention. The cell envelope of marine bacteria is in constant contact with the stressors of the surrounding environment, which implies necessarily that its main constituents (membrane lipids, proteins, and glycoconjugates) must be precisely organized to maintain the proper physiology and functionality, even in the “extreme” aquatic habitat. These membrane components must be versatile enough to face the constantly changing environment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
