Secretion of anti-biofilm activity by a marine Pseudoalteromonas strain

A review of: Klein, G. L., Soum-Soutera, E., Guede, Z., Bazire, A., Compere, C. & Dufour, A. (2011). The anti-biofilm activity secreted by a marine Pseudoalteromonas strain. Biofouling: The Journal of Bioadhesion and Biofilm Research. 27 (8), 931-940.

Bacterial biofilms are commonly recognised on submerged structures located in the marine environment. The development of these highly complex and diverse communities is strongly linked with numerous ecological advantages which can benefit a species, due to the various associations characterised by this constructive multi-species community. As a result, organisms which adopt this bacterial-lifestyle may exhibit increased levels of resistance against chemical substances and physical stresses.

Biofilm formation holds significant influence in a broad range of biological, medicinal and industrial applications. Several critical issues have been noted as being of particular importance in the marine environment such as; increased operational and maintenance costs due to fouling of ships hulls and the degradation of abiotic materials. Due to the substantial economic consequences related to their impact, current limitations in controlling marine biofilms support the incentive to explore novel sources of new compounds as an essential process in the development and application of innovative methods of regulation.

Anti-biofilm molecules isolated from marine bacteria are largely unknown. Nevertheless, certain bacteria such as Pseudoalteromonas produce a variety of compounds with the potential of biotechnological development. Based upon previous work conducted by the authors reporting the secretion of anti-biofilm activity by Pseudoalteromonas sp. 3J6, the study accumulates evidence in understanding whether the growth of Pseudoalteromonas sp. 3J6 permits the growth of Pseudoalteromonas in marine biofilms whilst inhibiting the development of biofilms by other marine bacteria.

A mixed biofilm inoculated with two Pseudoalteromonas strains; namely sp. 3J6 and D41 was grown. Characteristics of the growth and formation of the biofilm was monitored by confocal laser scanning microscope (CLSM) observations. Furthermore, an analysis of the spectra of action associated with each strain was made by a microtiter plate assay.

Building upon results noted by the authors in previous investigations, this study observed that Pseudoalteromonas sp. D41 also secretes anti-biofilm activity. CLSM observations identified the D41 strain to be largely predominant in a biofilm resulting from a co-inoculation by the two strains, subsequently distinguishing the biofilm as being increasingly similar to a single strain biofilm of D41 when compared to a single strain 3J6 biofilm. This observation advocates that the anti-biofilm molecules secreted by D41 can obstruct 3J6 growth during the formation of a mixed biofilm. Further analysis using the microtiter plate assay revealed that both 3J6 and D41 inhibited biofilm formation by 13 out of 18 marine bacteria. Nevertheless, differences in the spectra of action and the physical behaviours of the molecules between each strain was observed, suggesting that despite exhibiting similarities and holding a comparable impact in impeding biofilm formation of other bacteria, their methods are not identical.

Most of the anti-biofilm molecules currently described demonstrates anti-bacterial activity. However, during investigation of the anti-biofilm activity of both 3J6 and D41 in this study, an absence of any anti-bacterial properties was observed, rendering it ineffective against free-living bacteria and outlining its activity as being specifically directed against biofilms. The study shows the potential application of anti-biofilm molecules secreted by bacteria as promising constituents in aiding the development of methods controlling biofouling in the marine environment, whilst also holding a possible role in the characterisation of bacterial colonisation events and the structure and function of other marine aggregates characterised by interactions between the bacterial compositions of a community.