Lipopeptide biosurfactants fromPaenibacillus polymyxainhibit single and mixed species biofilms

Abstract

Although biofilms are recognised as important in microbial colonisation, solutions to their inhibition are predominantly based on planktonic assays. These solutions have limited efficacy against biofilms. Here, a series of biofilm-orientated tests were used to identify anti-biofilm compounds from marine micro-flora. This led to the isolation of a complex of anti-biofilm compounds from an extract of Paenibacillus polymyxa (PPE). A combination of rpHPLC and mass spectrometry identified the principle components of PPE as fusaricidin B (LI-FO4b) and polymyxin D1, with minor contributions from surfactins. This complex (PPE) reduced the biofilm biomass of Bacillus subtilis, Micrococcus luteus, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus bovis. In contrast, ampicillin was only effective against S. aureus. PPE also inhibited a self-assembling marine biofilm (SAMB) in co-incubation assays by 99.3% ± 1.9 and disrupted established SAMB by 72.4% ± 4.4, while ampicillin showed no significant reduction. The effectiveness of this complex of lipopeptides against single and multispecies biofilms suggests a future role in biofilm prevention strategies.

Microbial biofilms: biosurfactants as antibiofilm agents

“…Polymyxin E (colistin) is recommended as an early aggressive therapy to delay the onset of chronic P. aeruginosa infection (which frequently forms biofilms) or intermittent colonization in cystic fibrosis patients, a combination of oral ciprofloxacin with colistin inhalation (Doring et al 2000). Polymyxin D1 has been shown to be effective against mixed bacterial biofilms; however, our earlier work has shown that this compound was found in combination with fusaricidin and surfactin in undefined ratios (Quinn et al 2012). This complex of biosurfactants was also reported to inhibit the formation of biofilms of both Gram-positive bacteria such as S. aureus, Streptococcus bovis, Bacillus subtilis and Micrococcus luteus and Gram-negative bacteria such as P. aeruginosa.…”

“…This complex of biosurfactants was also reported to inhibit the formation of biofilms of both Gram-positive bacteria such as S. aureus, Streptococcus bovis, Bacillus subtilis and Micrococcus luteus and Gram-negative bacteria such as P. aeruginosa. Most interestingly, the biosurfactants were able to inhibit the formation of mixed species biofilms such as selfassembling marine biofilm (SAMB) in co-incubation assays by 99.3 % and disrupt previously established mixed SAMB by 72.4 % (Quinn et al 2012). …”

“…Since biofilms also grow slower than optimised planktonic conditions, the typical cultivation period for biofilms can vary from 4 h to 3--4 days or even 7-10 days in the case of slower growing environmental biofilms (Quinn et al 2012;Stepanovic et al 2007). Agitation considerations are equally important.…”

“…For planktonic MIC tests, organisms are seeded at a density of 1×10 6 /ml of fresh cells taken from the logarithmic stage of growth. In biofilm cultivation, seeding densities are typically a 1/100 dilution of a stationary phase culture (McLaughlin and Hoogewerf 2006;Quinn et al 2012). Some researchers use biofilm induction agents such as high glucose or alcohol to aid biofilm formation, but these may add unknown variables to the assay making the final biofilm data difficult to interpret.…”

“…In terms of temperature, the biofilm cultivation is carried out at the optimal temperature for biofilm growth of a particular species which may not be the same as the optimal temperature for planktonic growth; this could mean that biofilm cultivation may be at 20°C (even for clinical specimens) whilst others may be at 10°C in the cases of some environmental biofilms (Quinn et al 2012).…”