Abstract
AbstractManganese oxidizing marine microorganisms was studied from the coupons of PVC, Titanium, Brass, Copper and Stainless Steel were immersed one meter below water surface, using wooden rafts. The metal coupons, Brass, Titanium and Brass were exposed for a period of six months (October 2005 to March 2006). The PVC and SS were suspended in the sea for two months (February and March 2006). Sea water samples were also collected from the study area using water sampler to estimate the physiochemical and nutrients were analyzed. The population of HB and MHB on PVC was registered as 3.62 x 107 CFU/cm2 and 2.87 x 107 CFU/cm2, respectively while on Stainless Steel the population density of HB and MHB was recorded as 3.79 x 105 CFU/cm2 and 1.34 x 105 CFU/cm2. The PVC and titanium coupons were recorded relatively higher values comparing with other coupons, and it may be due to the non-toxic nature of the substratum. Brass also recorded higher bacterial population density compared to copper. The least population density observed in copper coupons could be due to it toxic nature. The generic composition of heterotrophic bacterial strains isolated from biofilm samples, both Gram-positive and Gram-negative groups were noted on all the materials studied. The notable thing was that Gram-positive group was fond to be dominant. The genera identified under Gram-positive were Bacillus sp., Staphylococcus sp. and Micrococcus sp. and the Gram-negative strains identified as Pseudomonas sp., Salmonella sp., Vibrio sp. and Proteus sp. Among the five types of coupons tested PVC exhibited highest Mn value of 5543 mg/g. Bacterial slim samples generated on the exposed coupons were scrapped and characterized by Bergey’s method.
Highlights
When any substrate surface is immersed in seawater, adhesion of many microorganisms is observed within a short time
The epiphytic nature of marine bacteria was first studied by Zobell and this bacterial adhesion leads the surfaces to corrosion of the material[2]
Sulphate-reducing bacteria and iron oxidizing bacteria have long been considered as major contributors of corrosion
Summary
The average population of Heterotrophic bacterial (HB) and Manganeseoxidizing heterotrophic bacterial (MHB). When comparing with other coupons the Brass showed higher population density of Gram-negative group than Gram-positive. Micrococcus sp., while the Gram-negative groups were identified as Pseudomonas sp., Salmonella sp., Vibrio sp. Micrococcus sp., while in Gram-negative group showed all the isolates except Salmonella sp. In brass Gramnegative strains were found to dominate over the Gram-positive by the genre Pseudomonas sp., Salmonella sp., Vibrio sp. The genera identified under Gram-positive included Bacillus sp., and Staphylococcus sp. In Gram-negative isolates were identified as Pseudomonas sp., and Vibrio sp., in copper coupons Salmonella sp. The generic composition of manganese-oxidizing heterotrophic bacteria isolated from the coupons of PVC, stainless steel, brass, titanium and copper was shows in the Table: 3. In general the bacterial strain isolated from all the coupons showed that Gram- positive groups were dominant.
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