Selective Bioaccumulation of Mixed Heavy Metals by a Range of Brackish Water Bacteria

Abstract

Heavy metals represent a significant source of pollution for the aquatic environment. The response of brackish water bacteria to increase concentrations of heavy metals were determined in seven bacterial species originally isolated from Lake Mariut, Alexandria, a heavily polluted lake. They were evaluated for their selectivity to accumulate a range of heavy metals including Fe, Zn, Cu, Pb, Ni and Co. Bacterial isolates identified as Pseudomonas cepacia, Enterobacter agglomerans, E. coli, Staphylococcus aureus and three Bacillus spp. B. licheniformis, B. alvei and B. cereus. They were gradually subjected to elevating levels of metals to evaluate their ability for metal bioaccumulation. The effect of heavy metals on bacterial growth was determined as % inhibition of the total viable count (TVC). The amount of accumulated metals (mg metal/g bacterial mass) was determined for each species every 24 hrs for 6 successive days. The selective uptake of metals depending on bacterial species as well as metal type where each species showed high affinity for at least two metals. This property could be efficiently used and manipulated in treatment processes for removing heavy metals. However, the tested bacteria showed more or less similar order of magnitude for metals uptake as Zn >Fe>Cr>Cu>Pb>Co>Ni which explained the toxicity of these metals with some exceptions.

Towards a Latin American and Caribbean international census of marine microbes (LACar ? ICoMM): overview and discussion on some current research directions

“…Moreover, the effectiveness of remediation agents to treat pesticides and hydrocarbon-polluted sediments may depend on a variety of environmental factors, including oxygen concentration, populations of indigenous bacteria, nutrient concentration and type of contamination (Rojas et al 1999). We examined the effects of pesticides consortium on the biodegradation of Aldrin by native estuarine bacteria and showed a 20% reduction in a period 30 days, similar results being reported by El-Bestawy (2000), who found a significant decrease in the rate of degradation and growth of microorganisms with chlorinated compounds in Lake Mariut, Alexandria, Egypt. Finally, the Guanabara Bay study focused in an ecosystem where long-term studies have been conducted since 1997, with a microbial observatory approach (MORio).…”