Evaluation of Different Salts and Heavy Metal Concentrations on Bacterial Biofilm from Selected Surface and Borehole Water Samples

Dibua Nwamaka Anthonia,Chude Charles Onuora,Chukwura Edna Ifeoma

doi:10.11648/j.fem.20200602.11

Dibua Nwamaka Anthonia, Chude Charles Onuora + Show 1 more

Open Access

https://doi.org/10.11648/j.fem.20200602.11

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Abstract

Biofilms in drinking water systems can serve as significant environmental reservoirs for pathogenic bacteria associated with gastro-enteric diseases. The evaluation of the effects of different salts and metal concentrations on bacterial biofilm from surface and borehole water samples was conducted. Water samples were collected, from 10 selected water sources of economic importance, aseptically using sterile containers. The physicochemical properties were investigated before the biofilm generation process. The collected water samples were allowed to stand in a secluded environment for four (4) weeks at 27°C±2°C for biofilm generation. The isolates were characterized culturally, morphologically, biochemically and molecularly. The isolates were identified as Stenotrophomonas pavanii, Stenotrophomonas maltophilia, Chromobacterium violaceum, Bacillus cereus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. It was observed that the isolates exhibited growth at a wide range of temperature, salts, pH, and metal salt concentrations. To determine the metal tolerance of the isolates, different concentrations (0.05, 0.1, 0.5, and 1.0%) of four metal salts; ferrous chloride (FeCl2), zinc chloride (ZnCl2), calcium chloride (CaCl2), and magnesium oxide (MgO) was used in nutrient broth. Their ability to grow in medium containing different salt (NaCl) concentrations was also evaluated. Different concentrations of NaCl ranging from 2.0% to 10.0% were used in nutrient broth seeded with 0.1ml of the inocula and incubated at 37°C for 48 and 24hours respectively. Growth was measured in terms of OD at 660 nm using spectrophotometer. Results showed a decline in the growth of the isolates with percentage increase in concentrations of all the metal salts. The result of the effect of NaCl salt on growth showed a decrease in growth with an increase in NaCl concentration from 2% to 10%. For Stenotrophomonas pavanii, FeCl2 is negatively correlated with pH r=-.998 but there is positive correlation between CaCl2 and NaCl with r=889.

Highlights

A biofilm is an assemblage of microbial cells in which cells adhere to each other on a surface
0.1ml of the inocula were seeded into tubes containing different concentrations of the metals and incubated at 37°C for 24hours
The bacterial isolates were identified as Stenotrophomonas pavanii, Stenotrophonmonas maltophilia Chromobacterium violaceum, Bacillus cereus, Bacillus subtillis, Escherichia coli, and Pseudomonas aeruginosa

Summary

Introduction

A biofilm is an assemblage of microbial cells in which cells adhere to each other on a surface. These adherent cells are enclosed in a self-produced matrix of extracellular polymeric substances (EPS) primarily composed of polysaccharide. An established biofilm structure comprises of microbial cells and EPS, has a defined architecture, and provides an optimal environment for the exchange of genetic materials between the cells. EPS may vary in chemical and physical properties, but it is primarily composed of polysaccharides. Some of these polysaccharides are neutral or polyanionic, as is the case of the EPS of Gram negative bacteria [6]

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