Myxococcus xanthus predation of Gram-positive or Gram-negative bacteria is mediated by different bacteriolytic mechanisms

• Published in: Applied and environmental microbiology Vol. 87; no. 5
• Main Authors: Arend, Kirstin I, Schmidt, Janka J, Bentler, Tim, Lüchtefeld, Carina, Eggerichs, Daniel, Hexamer, Hannah M, Kaimer, Christine
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.03.2021
• Subjects: Bacteria; Biomass energy production; Cell envelopes; Environmental Microbiology; Enzymes; Glycosidases; Glycoside hydrolase; Gram-negative bacteria; Hydrolase; In vivo methods and tests; Lysozyme; Mass spectrometry; Mass spectroscopy; Mode of action; Myxococcus xanthus; Predation; Prey; Proteins; Spotlight; Strains (organisms); glycoside hydrolase; bacterial behavior; outer membrane vesicles; bacteriolytic enzymes
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/AEM.02382-20

kills other species to use their biomass as energy source. Its predation mechanisms allow feeding on a broad spectrum of bacteria, but the identity of predation effectors and their mode of action remains largely unknown. We initially focused on the role of hydrolytic enzymes for prey killing and compared the activity of secreted proteins against four prey strains. 72 secreted proteins were identified by mass spectrometry, and among them a family 19 glycoside hydrolase that displayed bacteriolytic activity and This enzyme, which we name LlpM (lectin/lysozyme-like protein of ), was not essential for predation, indicating that additional secreted components are required to disintegrate prey. Furthermore, secreted proteins lysed only Gram-positive, but not Gram-negative species. We thus compared the killing of different preys by cell-associated mechanisms: Individual cells killed all four test strains in a cell-contact dependent manner, but were only able to disintegrate Gram-negative, not Gram-positive cell envelopes. Thus, our data indicate that uses different, multifactorial mechanisms for killing and degrading different preys. Besides secreted enzymes, cell-associated mechanisms that have not been characterized so far, appear to play a major role for prey killing. Predation is an important survival strategy of the widespread myxobacteria, but it remains poorly understood on the mechanistic level. Without a basic understanding of how prey cell killing and consumption is achieved, it also remains difficult to investigate the role of predation for the complex myxobacterial lifestyle, reciprocal predator-prey relationships or the impact of predation on complex bacterial soil communities.We study predation in the established model organism , aiming to dissect the molecular mechanisms of prey cell lysis. In this study, we addressed the role of secreted bacteriolytic proteins, as well as potential mechanistic differences in the predation of Gram-positive and Gram-negative bacteria. Our observation shows that secreted enzymes are sufficient for killing and degrading Gram-positive species, but that cell-associated mechanisms may play a major role for killing Gram-negative and Gram-positive prey on fast timescales.