Biofilm Formation by the Fish Pathogen Flavobacterium columnare: Development and Parameters Affecting Surface Attachment

Abstract

bFlavobacterium columnare is a bacterial fish pathogen that affects many freshwater species worldwide. The natural reservoir of this pathogen is unknown, but its resilience in closed aquaculture systems posits biofilm as the source of contagion for farmed fish. The objectives of this study were (i) to characterize the dynamics of biofilm formation and morphology under static and flow conditions and (ii) to evaluate the effects of temperature, pH, salinity, hardness, and carbohydrates on biofilm formation. Nineteen F. columnare strains, including representatives of all of the defined genetic groups (genomovars), were compared in this study. The structure of biofilm was characterized by light microscopy, confocal laser scanning microscopy, and scanning electron microscopy. F. columnare was able to attach to and colonize inert surfaces by producing biofilm. Surface colonization started within 6 h postinoculation, and microcolonies were observed within 24 h. Extracellular polysaccharide substances and water channels were observed in mature biofilms (24 to 48 h). A similar time course was observed when F. columnare formed biofilm in microfluidic chambers under flow conditions. The virulence potential of biofilm was confirmed by cutaneous inoculation of channel catfish fingerlings with mature biofilm. Several physicochemical parameters modulate attachment to surfaces, with the largest influence being exerted by hardness, salinity, and the presence of mannose. Maintenance of hardness and salinity values within certain ranges could prevent biofilm formation by F. columnare in aquaculture systems.

Analysis of biofilm formation by intestinal lactobacilli

“…Several factors including sugar metabolism may lead to modified biofilm formation (Jin et al 2004;Chai et al 2012;Cai et al 2013). In line with work presented here, L. rhamnosus GG and vaginal lactobacilli were not able to form biofilm after 24 or 96 h culture in standard culture media used for lactic acid bacteria where polystyrene microplates were used (Lebeer et al 2007;Terraf et al 2012).…”

Gamete-associated flavobacteria of the oviparous Chinook salmon (Oncorhynchus tshawytscha) in lakes Michigan and Huron, North America

“…colonizing lake sturgeon (Acipenser fulvescens) egg surfaces following surface disinfection with iodine was also recently reported (Chalupnicki et al, 2015). The persistence of flavobacteria after surface disinfection could be due to a number of factors, including: a) the ability to form biofilm, which is known to occur in Flavobacterium (Cai et al, 2013) and Chryseobacterium spp. (Lo and Chang, 2014) and that facilitates bacterial survival when exposed to chemotherapeutic treatments (Sundell and Wiklund, 2011); b) the presence of high quantities of bacteria, which can lead to bacterial survival during iodophor disinfection (Cipriano et al, 2001); c) intra-ova transmission, which would shelter the flavobacteria from iodophor exposure while inside the egg and that has been documented for some fish-pathogenic flavobacteria (e.g., F. psychrophilum, Brown et al, 1997;Cipriano, 2015); d) resistance to iodophor, which is interesting in light of the fact that Chryseobacterium spp.…”

Physiology and immunology of mucosal barriers in catfish (Ictalurus spp.)

“…33 A recent study of F. columnare biofilm formation highlighted the importance of factors such as salinity, water hardness, and the presence of sugars such as mannose, all directly relevant to mucus production. [34][35][36][37] Mucins in the skin The skin in fish is constantly processing complex signals from the aquatic milieu, sensing and integrating environmental, nutritional, and health cues. In fish, mucus is also continuously secreted by goblet cells in the skin epidermis, playing indispensable roles in shedding pathogen and dead cells away to maintain host health.…”