ABSTRACT
Biofilm genesis by Pseudomonas and Staphylococcus sp is associated with biofouling in natural settings. D-Tryptophan (DTrp) inhibits bacterial biofilms and have been proposed for biofouling control applications. In this study, D-Trp significantlyinhibited Pseudomonas mendocina and Staphylococcus aureus cell attachment (biofilm formation) rates on polystyrene96-well microtiter plates in comparison with L-Tryptophan (L-Trp) and mixtures of D-/L-Tryptophan (D-/L-Trp). Theinhibitory effect was greater on P. mendocina, where the rate of cell adherence was declined to 8.7 9 105 cells/h from8.0 9 106 cells/h (control) in P. mendocina. In S. aureus it was declined to 4.2 9 107 cells/h from 9.2 9 107 cells/h(control) at 1 mM concentration. It hindered the intracellular communication and adherence in both the strains, as confirmed by SEM and real time PCR analysis. Addition of D-Trp to preformed biofilms also caused partial disassembly. Intraand interbacterial aggregation were decreased subsequently upon treatment with D-Trp. It repressed the genes involved incell–cell communication, which could be responsible for the diminished biofilm formation of the selected strains. HenceD-Tryptophan has proved to be an effective strategy to control biofilm and may support in the development of surfacecoating technologies.
ABSTRACT
Microcystis thrive in eutrophic water bodies laden with toxins and metabolites that adversely affect the water quality. In the present study, attempts have been made to demonstrate inhibition of Microcystis growth and degradation of its toxin (microcystin) by three algalytic bacterial isolates, viz.; Rhizobium sp. (MF185100), Methylobacterium zatmanii (MF185099), Sandaracinobactor sibiricus (MF185098). Microcystis aeruginosa was collected from eutrophic lake of Central India and purified by sequential antibiotic (ampicillin, kanamycin and imipenem) treatment. Purified Microcystis culture was subjected to bacterial interactions for understanding algalytic activity. It was observed that interaction of consortia of three isolated bacteria as mentioned above showed 95% Microcystis lysis in BG-II media as analyzed spectrophotometrically (OD678 nm). The 16S rDNA sequence analysis of consortia members showed their phylogenetic relationship with reported algicidal Rhizobiaceae and Dermabacteraceae. Interestingly, one consortia member viz. Rhizobium sp. (MF185100) was capable of utilizing Microcystis toxin as sole carbon source for its growth. Interaction studies of Microcystis and algalytic bacteria revealed gradual decrease (>95% degradation in 25 days) in microcystin toxin concentration as revealed through HPLC analysis. The present study, thus proposes using algicidal bacteria for sustainable mitigation of Microcystis found trapped in cyanobacterial harmful algal bloom (HAB).