Mechanisms for Pseudoalteromonas piscicida-Induced Killing of Vibrios and Other Bacterial Pathogens

Abstract

is a Gram-negative gammaproteobacterium found in the marine environment. Three strains of pigmented were isolated from seawater and partially characterized by inhibition studies, electron microscopy, and analysis for proteolytic enzymes. Growth inhibition and death occurred around colonies of on lawns of the naturally occurring marine pathogens ,, ,, and Inhibition also occurred on lawns of but not on O157:H7 or serovar Typhimurium. Inhibition was not pH associated, but it may have been related to the secretion of a cysteine protease with strong activity, as detected with a synthetic fluorogenic substrate. This diffusible enzyme was secreted from all three strains. Direct overlay of the colonies with synthetic fluorogenic substrates demonstrated the activity of two aminopeptidase Bs, a trypsin-like serine protease, and enzymes reactive against substrates for cathepsin G-like and caspase 1-like proteases. In seawater cultures, scanning electron microscopy revealed numerous vesicles tethered to the outer surface of and a novel mechanism of direct transfer of these vesicles to Vesicles digested holes in cells, while the congregated around the vibrios in a predatory fashion. This transfer of vesicles and vesicle-associated digestion of holes were not observed in other bacteria, suggesting that vesicle binding may be mediated by host-specific receptors. In conclusion, we show two mechanisms by which inhibits and/or kills competing bacteria, involving the secretion of antimicrobial substances and the direct transfer of digestive vesicles to competing bacteria. species are widespread in nature and reduce competing microflora by the production of antimicrobial compounds. We isolated three strains of and characterized secreted and cell-associated proteolytic enzymes, which may have antimicrobial properties. We identified a second method by which kills It involves the direct transfer of apparently lytic vesicles from the surface of the strains to the surface of cells, with subsequent digestion of holes in the cell walls. Enzymes associated with these vesicles are likely responsible for the digestion of holes in the cell walls. has potential applications in aquaculture and food safety, in control of the formation of biofilms in the environment, and in food processing. These findings may facilitate the probiotic use of to inactivate pathogens and may lead to the isolation of enzymes and other antimicrobial compounds of pharmacological value.

Antibiotic-induced alterations and repopulation dynamics of yellowtail kingfish microbiota

“…With other dominant constituents found here (e.g. Pseudoalteromonas) also reported to comprise both pathogenic [57] and bene cial (probiotic-like) species [58][59][60][61] questions thus remain around their role and changes in abundance between cultivation systems and requires further elucidation, particularly given the inability to resolve many of the ASVs to a species level in this study.…”

Local Conditions Influence the Prokaryotic Communities Associated With the Mesophotic Black Coral Antipathella subpinnata

“…Some A. subpinnata -associated bacteria, for example Pseudoalteromonas , may have a microbiome regulatory role. These bacteria are often found in association with marine animals, including cnidarians, and are known to secrete compounds with antibacterial ( Holmström and Kjelleberg, 1999 ; Shnit-Orland et al, 2012 ; Richards et al, 2017 ), antifungal ( Shiroyama et al, 2017 ) and alginolytic ( Holmström and Kjelleberg, 1999 ) activities. Besides, Endozoicomonas ( Neave et al, 2016 ) and Actinobacteria (phylum including Propionibacterium ) ( Ritchie, 2006 ; Nithyanand et al, 2011 ; Krediet et al, 2013 ; Zhang et al, 2013 ) have been implicated in coral microbiome regulation.…”

Probiotic Bacteria as an Healthy Alternative for Fish Aquaculture

“…As well as small (peptide)/major (protein) bacteriocins; lysozyme; proteases and hydrogen peroxide) [9,28,31]. Or secretion of antimicrobial proteolytic enzymes (aminopeptidase Bs, trypsin-like serine protease, and enzymes reactive against substrates for cathepsin G-and caspase 1-like proteases) [32] -Resistant to bile salts and low pH: one of the routes of introduction of the probiotic is through food [28] - Rapid growth and adequate to host/crop temperature [28] - Capacity of adhesion and compete for adhesion sites: modulates the host's microbiota [9,31,33] -Improve host immune response [9,31,[34][35][36]. When a pathogen enters the body, the adaptive immune system (B cell and T cell responses) and the complement system are activated [37][38][39].…”