Alterocin, an Antibiofilm Protein Secreted by Pseudoalteromonas sp. Strain 3J6

Anti-Biofilm Extracts and Molecules from the Marine Environment

Pathogenic bacteria and their biofilms are involved in many diseases and represent a major public health problem, including the development of antibiotic resistance. These biofilms are known to cause chronic infections for which conventional antibiotic treatments are often ineffective. The search for new molecules and innovative solutions to combat these pathogens and their biofilms has therefore become an urgent need. The use of molecules with anti-biofilm activity would be a potential solution to these problems. The marine world is rich in micro- and macro-organisms capable of producing secondary metabolites with original skeletons. An interest in the chemical strategies used by some of these organisms to regulate and/or protect themselves against pathogenic bacteria and their biofilms could lead to the development of bioinspired, eco-responsible solutions. Through this original review, we listed and sorted the various molecules and extracts from marine organisms that have been described in the literature as having strictly anti-biofilm activity, without bactericidal activity.

The natriuretic peptide receptor agonist osteocrin disperses Pseudomonas aeruginosa biofilm

Biofilms are highly tolerant to antimicrobials and host immune defense, enabling pathogens to thrive in hostile environments. The diversity of microbial biofilm infections requires alternative and complex treatment strategies. In a previous work we demonstrated that the human Atrial Natriuretic Peptide (hANP) displays a strong anti-biofilm activity toward Pseudomonas aeruginosa and that the binding of hANP by the AmiC protein supports this effect. This AmiC sensor has been identified as an analog of the human natriuretic peptide receptor subtype C (h-NPRC). In the present study, we evaluated the anti-biofilm activity of the h-NPRC agonist, osteocrin (OSTN), a hormone that displays a strong affinity for the AmiC sensor at least in vitro. Using molecular docking, we identified a pocket in the AmiC sensor that OSTN reproducibly docks into, suggesting that OSTN might possess an anti-biofilm activity as well as hANP. This hypothesis was validated since we observed that OSTN dispersed established biofilm of P. aeruginosa PA14 strain at the same concentrations as hANP. However, the OSTN dispersal effect is less marked than that observed for the hANP (-61% versus -73%). We demonstrated that the co-exposure of P. aeruginosa preformed biofilm to hANP and OSTN induced a biofilm dispersion with a similar effect to that observed with hANP alone suggesting a similar mechanism of action of these two peptides. This was confirmed by the observation that OSTN anti-biofilm activity requires the activation of the complex composed by the sensor AmiC and the regulator AmiR of the ami pathway. Using a panel of both P. aeruginosa laboratory reference strains and clinical isolates, we observed that the OSTN capacity to disperse established biofilms is highly variable from one strain to another. Taken together, these results show that similarly to the hANP hormone, OSTN has a strong potential to be used as a tool to disperse P. aeruginosa biofilms.

Potential of Marine Strains of Pseudoalteromonas to Improve Resistance of Juvenile Sea Bass to Pathogens and Limit Biofilm Development

The European sea bass (Dicentrarchus labrax), one of the most produced marine fish species in Europe, is acutely vulnerable to multiple infectious hazards. In this study, we investigated the potential probiotic effect of some marine Pseudoalteromonas bacterial strains against two major pathogens of this species, Vibrio harveyi and the nervous necrosis virus (NNV), and examined their antibiofilm effect. Impregnation phase was done by repeated immersion of juvenile's sea bass during 8 to 12 weeks in seawater containing the probiotic candidates at a concentration of 106 CFU/mL. Four candidates were tested: (1) a combination of two strains producing antimicrobial compounds, hCg-42 and hOe-125; (2) strain 3J6, with known antibiofilm properties; (3) strain RA15, from the same genus, but with no identified probiotic effect; and (4) a control group without probiotics. At the end of the impregnation phase, fish underwent an infection challenge with V. harveyi or with a pathogenic strain of NNV and mortality was monitored. For the V. harveyi challenge, improved survival rates of 10 and 25% were obtained for the RA15 and the mix hCg-42 + hOe-125-impregnated groups, respectively. For the NNV challenge, no significant benefic effect of the probiotics on infection kinetics or cumulative mortality was observed. At the end of the impregnation phase, the maximal thickness of biofilm was significantly lower in the 3J6, double strain, and RA15 groups, compared with the non-impregnated control group. This study highlights the interesting probiotic potential of marine bacteria to limit mortalities induced by bacterial pathogens as well as biofilm development.

Therapeutic Potential of Marine Probiotics: A Survey on the Anticancer and Antibacterial Effects of Pseudoalteromonas spp

Due to the increasing limitations and negative impacts of the current options for preventing and managing diseases, including chemotherapeutic drugs and radiation, alternative therapies are needed, especially ones utilizing and maximizing natural products (NPs). NPs abound with diverse bioactive primary and secondary metabolites and compounds with therapeutic properties. Marine probiotics are beneficial microorganisms that inhabit marine environments and can benefit their hosts by improving health, growth, and disease resistance. Several studies have shown they possess potential bioactive and therapeutic actions against diverse disease conditions, thus opening the way for possible exploitation of their benefits through their application. Pseudoalteromonas spp. are a widely distributed heterotrophic, flagellated, non-spore-forming, rod-shaped, and gram-negative marine probiotic bacteria species with reported therapeutic capabilities, including anti-cancer and -bacterial effects. This review discusses the basic concepts of marine probiotics and their therapeutic effects. Additionally, a survey of the anticancer and antibacterial effects of Pseudoalteromonas spp. is presented. Finally, marine probiotic production, advances, prospects, and future perspectives is presented.

Extracts from Wallis Sponges Inhibit Vibrio harveyi Biofilm Formation

Pathogenic bacteria and their biofilms are involved in many human and animal diseases and are a major public health problem with, among other things, the development of antibiotic resistance. These biofilms are known to induce chronic infections for which classical treatments using antibiotic therapy are often ineffective. Sponges are sessile filter-feeding marine organisms known for their dynamic symbiotic partnerships with diverse microorganisms and their production of numerous metabolites of interest. In this study, we investigated the antibiofilm efficacy of different extracts from sponges, isolated in Wallis, without biocidal activity. Out of the 47 tested extracts, from 28 different genera, 11 showed a strong activity against Vibrio harveyi biofilm formation. Moreover, one of these extracts also inhibited two quorum-sensing pathways of V. harveyi.

Exploring Oceans for Curative Compounds: Potential New Antimicrobial and Anti-Virulence Molecules against Pseudomonas aeruginosa

Although several antibiotics are already widely used against a large number of pathogens, the discovery of new antimicrobial compounds with new mechanisms of action is critical today in order to overcome the spreading of antimicrobial resistance among pathogen bacteria. In this regard, marine organisms represent a potential source of a wide diversity of unique secondary metabolites produced as an adaptation strategy to survive in competitive and hostile environments. Among the multidrug-resistant Gram-negative bacteria, Pseudomonas aeruginosa is undoubtedly one of the most important species due to its high intrinsic resistance to different classes of antibiotics on the market and its ability to cause serious therapeutic problems. In the present review, we first discuss the general mechanisms involved in the antibiotic resistance of P. aeruginosa. Subsequently, we list the marine molecules identified up until now showing activity against P. aeruginosa, dividing them according to whether they act as antimicrobial or anti-virulence compounds.

Molecular Relationships in Biofilm Formation and the Biosynthesis of Exoproducts in Pseudoalteromonas spp

Most members of the Pseudoalteromonas genus have been isolated from living surfaces as members of epiphytic and epizooic microbiomes on marine macroorganisms. Commonly Pseudoalteromonas isolates are reported as a source of bioactive exoproducts, i.e., secondary metabolites, such as exopolymeric substances and extracellular enzymes. The experimental conditions for the production of these agents are commonly associated with sessile metabolic states such as biofilms or liquid cultures in the stationary growth phase. Despite this, the molecular mechanisms that connect biofilm formation and the biosynthesis of exoproducts in Pseudoalteromonas isolates have rarely been mentioned in the literature. This review compiles empirical evidence about exoproduct biosynthesis conditions and molecular mechanisms that regulate sessile metabolic states in Pseudoalteromonas species, to provide a comprehensive perspective on the regulatory convergences that generate the recurrent coexistence of both phenomena in this bacterial genus. This synthesis aims to provide perspectives on the extent of this phenomenon for the optimization of bioprospection studies and biotechnology processes based on these bacteria.

Anti-Biofilm Activity of a Low Weight Proteinaceous Molecule from the Marine Bacterium Pseudoalteromonas sp. IIIA004 against Marine Bacteria and Human Pathogen Biofilms

Pseudoalteromonas bacteria are known as potential bioactive metabolite producers. Because of the need to obtain natural molecules inhibiting the bacterial biofilms, we investigated the biofilm inhibitory activity of the marine bacterium Pseudoalteromonas sp. IIIA004 against the pioneer surface colonizer Roseovarius sp. VA014. The anti-biofilm activity from the culture supernatant of Pseudoalteromonas sp. IIIA004 (SNIIIA004) was characterized in microtiter plates (static conditions/polystyrene surface) and in flow cell chambers (dynamic conditions/glass surface). The Pseudoalteromonas exoproducts exhibited an inhibition of Roseovarius sp. VA014 biofilm formation as well as a strong biofilm dispersion, without affecting the bacterial growth. Microbial adhesion to solvent assays showed that SNIIIA004 did not change the broad hydrophilic and acid character of the Roseovarius strain surface. Bioassay-guided purification using solid-phase extraction and C18 reverse-phase-high-performance liquid chromatography (RP-HPLC) was performed from SNIIIA004 to isolate the proteinaceous active compound against the biofilm formation. This new anti-biofilm low weight molecule (< 3kDa), named P004, presented a wide spectrum of action on various bacterial biofilms, with 71% of sensitive strains including marine bacteria and human pathogens. Pseudoalteromonas sp. IIIA004 is a promising source of natural anti-biofilm compounds that combine several activities.