RESUMO
The dinoflagellate Prorocentrum triestinum forms high biomass blooms that discolor the water (red tides), which may pose a serious threat to marine fauna and aquaculture exploitations. In this study, the algicidal effect of a bacterial strain (0YLH) belonging to the genus Shewanella was identified and evaluated against P. triestinum. The algicidal effects on the dinoflagellate were observed when P. triestinum was exposed to cell-free supernatant (CFS) from stationary-phase cultures of the 0YLH strain. After 24 h exposure, a remarkable reduction in the photosynthetic efficiency of P. triestinum was achieved (55.9%), suggesting the presence of extracellular bioactive compounds produced by the bacteria with algicidal activity. Furthermore, the CFS exhibited stability and maintained its activity across a wide range of temperatures (20-120 °C) and pH values (3-11). These findings highlight the algicidal potential of the bacterium Shewanella halifaxensis 0YLH as a promising tool for the environmentally friendly biological control of P. triestinum blooms.
Assuntos
Dinoflagellida , Shewanella , Proliferação Nociva de Algas , AquiculturaRESUMO
Biofouling refers to the undesirable growth of microorganisms on water-submerged surfaces. Microfouling, the initial state of biofouling, is characterized by aggregates of microbial cells enclosed in a matrix of extracellular polymeric substances (EPSs). In seawater desalination plants, filtration systems, such as reverse-osmosis membranes (ROMs), are affected by microfouling, which decreases their efficiency in obtaining permeate water. The existing chemical and physical treatments are expensive and ineffective; therefore, controlling microfouling on ROMs is a considerable challenge. Thus, new approaches are necessary to improve the current ROM cleaning treatments. This study demonstrates the application of Alteromonas sp. Ni1-LEM supernatant as a cleaning agent for ROMs in a desalination seawater plant in northern Chile (Aguas Antofagasta S.A.), which is responsible for supplying drinking water to the city of Antofagasta. ROMs treated with Altermonas sp. Ni1-LEM supernatant exhibited statistically significant results (p < 0.05) in terms of seawater permeability (Pi), permeability recovery (PR), and the conductivity of permeated water compared with control biofouling ROMs and those treated with the chemical cleaning protocol applied by the Aguas Antofagasta S.A. desalination plant.
RESUMO
Biofouling control in reverse osmosis membranes (ROMs) is challenging due to the high cost of treatments, and reduction in the life of ROMs. This study characterizes the biofouling in the ROMs from a desalination plant and reports its effective removal using the supernatant obtained from Alteromonas sp. strain Ni1-LEM. The characterization of the bacterial community revealed that the most abundant taxa in ROMs were the genera Fulvivirga and Pseudoalteromonas, and unclassified species of the families Flavobacteriaceae and Sphingomonadaceae. This bacterial community significantly decreased upon treatment with the supernatant from Alteromonas sp. Ni1-LEM, resulting in the prevalence of the genus Pseudoalteromonas. Furthermore, this bacterial supernatant significantly inhibited cell adhesion of seven benthic microalgae isolated from ROMs as well as promoting cell detachment of the existing microbial biofilms. The study showed that the extracellular supernatant modified the conformation of extracellular polymeric substances (EPS) in the biofouling of ROMs without any biocidal effects.