Search

Copyright © 2016 Thøgersen, Delpin, Melchiorsen, Kilstrup, Månsson, Bunk, Spröer, Overmann, Nielsen and Gram. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms., It has previously been reported that some strains of the marine bacterium Pseudoalteromonas luteoviolacea produce the purple bioactive pigment violacein as well as the antibiotic compound indolmycin, hitherto only found in Streptomyces. The purpose of the present study was to determine the relative role of each of these two compounds as antibacterial compounds in P. luteoviolacea S4054. Using Tn10 transposon mutagenesis, a mutant strain that was significantly reduced in violacein production in mannose-containing substrates was created. Full genome analyses revealed that the vio-biosynthetic gene cluster was not interrupted by the transposon; instead the insertion was located to the maeA gene encoding the malic enzyme. Supernatant of the mutant strain inhibited Vibrio anguillarum and Staphylococcus aureus in well diffusion assays and in MIC assays at the same level as the wild type strain. The mutant strain killed V. anguillarum in co-culture experiments as efficiently as the wild type. Using UHPLC-UV/Vis analyses, we quantified violacein and indolmycin, and the mutant strain only produced 7–10% the amount of violacein compared to the wild type strain. In contrast, the amount of indolmycin produced by the mutant strain was about 300% that of the wild type. Since inhibition of V. anguillarum and S. aureus by the mutant strain was similar to that of the wild type, it is concluded that violacein is not the major antibacterial compound in P. luteoviolacea. We furthermore propose that production of violacein and indolmycin may be metabolically linked and that yet unidentified antibacterial compound(s) may be play a role in the antibacterial activity of P. luteoviolacea.

The chitinase gene cluster of the marine bacterium Pseudoalteromonas sp. S91, chiABC, which produces the major chitinases of this sp., was transcribed as an operon and from each individual gene. chiA, chiB and chiC were found to possess multiple transcriptional start points (TSPs), the use of which was determined by the nutrient regime used for S91 growth. In minimal medium containing glutamate, chiA, chiB and chiC each used 3, 1 and 1 TSP, respectively. Upon the addition of the chitin monomer N-acetylglucosamine, the number of chiA TSPs was unaffected. However, chiB used an additional 4 TSPs, and chiC used four new TSPs excluding the TSP used in glutamate only. In addition, the cluster was transcribed as an operon from TSP A1 of chiA. All TSPs were potentially associated with either a sigma(70)-or sigma(54)-dependent promoter. Under the growth conditions used, no TSPs were detected for chiB or chiC in S91CX, a chiA transposon mutant. The transcription of the S91 chiABC gene cluster produced at least four polycistronic mRNAs. In addition, the occurrence of operon transcription of chiABC, and identification of an additional 12 putative TSPs within the gene cluster, gave an indication that each gene appeared to be transcribed from more than one promoter region upstream of each in-frame translation start codon. Questions arose regarding the reason for this complexity of transcription within the gene cluster, leading to a re-evaluation of the Chi protein domains. By bioinformatic review, ChiA, ChiB and ChiC were found to potentially possess additional putative domains. he ISME Journal (2009) 3, 1053-1063; doi:10.1038/ismej.2009.54; published online 21 May 2009 Refereed/Peer-reviewed

Antifouling strategies to limit biofilms on submerged surfaces in the marine environment are of particular interest due to the economic and environmental impacts in industries such as shipping and aquaculture. Here, we investigate the influence of chemically modified hessian bag surfaces on the bacterial abundance and community composition of biofilm formation using flow cytometry and 16S rRNA pyrosequencing. Hessian bags were coated with 5% and 10% Propyl(trimethoxy) silane (PTMS) and half of the bags had their lignin and hemicellulose removed via NaOH mercerisation. Significantly lower bacterial abundance was observed on mercerised bags treated with 5% PTMS (p < 0.01). Significant shifts in bacterial taxa were also observed (p = 0.0004), whereby unmercerised bags exhibited higher relative abundances of the anaerobic family Desulfovibrionaceae (4.5 +/- 1.7%), while mercerised bags displayed higher relative abundances of the aerobic family Phyllobacteriaceae (3.6 +/- 1.7%). This suggests that the mercerisation process may lower colonization rates and subsequently produce a thinner biofilm. This hypothesis is strengthened by the lower abundance of bacteria on mercerised bags, particularly on the 5% PTMS coating. Our results show that modifying a hessian surface via non-toxic coating and mercerisation reduces biofilm formation and also shifts the dominant taxa, increasing our understanding of antifouling strategies in the marine environment. (C) 2015 Elsevier B.V. All rights reserved. Refereed/Peer-reviewed