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Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture
BACKGROUND: Hypervirulent Aeromonas hydrophila (vAh) is an emerging pathogen in freshwater aquaculture that results in the loss of over 3 million pounds of marketable channel catfish, Ictalurus punctatus, and channel catfish hybrids (I. punctatus, ♀ x blue catfish, I. furcatus, ♂) each year from fre...
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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BioMed Central
2021
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7788984/ https://www.ncbi.nlm.nih.gov/pubmed/33407117 http://dx.doi.org/10.1186/s12866-020-02065-2 |
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author | Barger, Priscilla C. Liles, Mark R. Beck, Benjamin H. Newton, Joseph C. |
author_facet | Barger, Priscilla C. Liles, Mark R. Beck, Benjamin H. Newton, Joseph C. |
author_sort | Barger, Priscilla C. |
collection | PubMed |
description | BACKGROUND: Hypervirulent Aeromonas hydrophila (vAh) is an emerging pathogen in freshwater aquaculture that results in the loss of over 3 million pounds of marketable channel catfish, Ictalurus punctatus, and channel catfish hybrids (I. punctatus, ♀ x blue catfish, I. furcatus, ♂) each year from freshwater catfish production systems in Alabama, U.S.A. vAh isolates are clonal in nature and are genetically unique from, and significantly more virulent than, traditional A. hydrophila isolates from fish. Even with the increased virulence, natural infections cannot be reproduced in aquaria challenges making it difficult to determine modes of infection and the pathophysiology behind the devastating mortalities that are commonly observed. Despite the intimate connection between environmental adaptation and plastic response, the role of environmental adaption on vAh pathogenicity and virulence has not been previously explored. In this study, secreted proteins of vAh cultured as free-living planktonic cells and within a biofilm were compared to elucidate the role of biofilm growth on virulence. RESULTS: Functional proteolytic assays found significantly increased degradative activity in biofilm secretomes; in contrast, planktonic secretomes had significantly increased hemolytic activity, suggesting higher toxigenic potential. Intramuscular injection challenges in a channel catfish model showed that in vitro degradative activity translated into in vivo tissue destruction. Identification of secreted proteins by HPLC-MS/MS revealed the presence of many putative virulence proteins under both growth conditions. Biofilm grown vAh produced higher levels of proteolytic enzymes and adhesins, whereas planktonically grown cells secreted higher levels of toxins, porins, and fimbrial proteins. CONCLUSIONS: This study is the first comparison of the secreted proteomes of vAh when grown in two distinct ecological niches. These data on the adaptive physiological response of vAh based on growth condition increase our understanding of how environmental niche partitioning could affect vAh pathogenicity and virulence. Increased secretion of colonization factors and degradative enzymes during biofilm growth and residency may increase bacterial attachment and host invasiveness, while increased secretion of hemolysins, porins, and other potential toxins under planktonic growth (or after host invasion) could result in increased host mortality. The results of this research underscore the need to use culture methods that more closely mimic natural ecological habitat growth to improve our understanding of vAh pathogenesis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12866-020-02065-2. |
format | Online Article Text |
id | pubmed-7788984 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2021 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-77889842021-01-07 Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture Barger, Priscilla C. Liles, Mark R. Beck, Benjamin H. Newton, Joseph C. BMC Microbiol Research Article BACKGROUND: Hypervirulent Aeromonas hydrophila (vAh) is an emerging pathogen in freshwater aquaculture that results in the loss of over 3 million pounds of marketable channel catfish, Ictalurus punctatus, and channel catfish hybrids (I. punctatus, ♀ x blue catfish, I. furcatus, ♂) each year from freshwater catfish production systems in Alabama, U.S.A. vAh isolates are clonal in nature and are genetically unique from, and significantly more virulent than, traditional A. hydrophila isolates from fish. Even with the increased virulence, natural infections cannot be reproduced in aquaria challenges making it difficult to determine modes of infection and the pathophysiology behind the devastating mortalities that are commonly observed. Despite the intimate connection between environmental adaptation and plastic response, the role of environmental adaption on vAh pathogenicity and virulence has not been previously explored. In this study, secreted proteins of vAh cultured as free-living planktonic cells and within a biofilm were compared to elucidate the role of biofilm growth on virulence. RESULTS: Functional proteolytic assays found significantly increased degradative activity in biofilm secretomes; in contrast, planktonic secretomes had significantly increased hemolytic activity, suggesting higher toxigenic potential. Intramuscular injection challenges in a channel catfish model showed that in vitro degradative activity translated into in vivo tissue destruction. Identification of secreted proteins by HPLC-MS/MS revealed the presence of many putative virulence proteins under both growth conditions. Biofilm grown vAh produced higher levels of proteolytic enzymes and adhesins, whereas planktonically grown cells secreted higher levels of toxins, porins, and fimbrial proteins. CONCLUSIONS: This study is the first comparison of the secreted proteomes of vAh when grown in two distinct ecological niches. These data on the adaptive physiological response of vAh based on growth condition increase our understanding of how environmental niche partitioning could affect vAh pathogenicity and virulence. Increased secretion of colonization factors and degradative enzymes during biofilm growth and residency may increase bacterial attachment and host invasiveness, while increased secretion of hemolysins, porins, and other potential toxins under planktonic growth (or after host invasion) could result in increased host mortality. The results of this research underscore the need to use culture methods that more closely mimic natural ecological habitat growth to improve our understanding of vAh pathogenesis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12866-020-02065-2. BioMed Central 2021-01-06 /pmc/articles/PMC7788984/ /pubmed/33407117 http://dx.doi.org/10.1186/s12866-020-02065-2 Text en © The Author(s) 2021 Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. |
spellingShingle | Research Article Barger, Priscilla C. Liles, Mark R. Beck, Benjamin H. Newton, Joseph C. Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture |
title | Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture |
title_full | Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture |
title_fullStr | Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture |
title_full_unstemmed | Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture |
title_short | Differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent Aeromonas hydrophila under biofilm and planktonic culture |
title_sort | differential production and secretion of potentially toxigenic extracellular proteins from hypervirulent aeromonas hydrophila under biofilm and planktonic culture |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7788984/ https://www.ncbi.nlm.nih.gov/pubmed/33407117 http://dx.doi.org/10.1186/s12866-020-02065-2 |
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