Savage Stainless

Savage Stainless

Biofouling of Manganese-oxidizing Microorganisms in Rameswaram

When any substrate surface is immersed in seawater, adhesion of many microorganisms is observed within a short time. This initial covering of exposed surface is called the slim, biofilm or primary film. Once this attachment process is initiated, a succession of settling of organisms is observed leading to the development microbial population. The predominant organisms are bacteria, algae, unicellular fungi and protozoa in a matrix of detritus, which provides a continuous source of nourishment1. The epiphytic nature of marine bacteria was first studied by Zobell and this bacterial adhesion leads the surfaces to corrosion of the material2. Fouling refers to the undesirable formation of deposits on equipment surfaces, which significantly decreases equipment’s performance and/or its useful life.  Several types of fouling and their combinations may occur, including biological, corrosion, particulate and precipitation fouling.  In general, more than one type of fouling will be occurring simultaneously3.

A sequence of discrete events occurs in the development of biofilms on clean surfaces when they are immersed in the marine environment4.

1.  Adsorption of an abiotic conditioning film.

2. Approach of bacteria to the conditioned surface through water movement, diffusion and/or motility.

3. Reversible adhesion of both motile and non-motile bacteria.

4.  Irreversible adhesion of bacteria mediated by bacteria polymers, and

5.  Development of a secondary microflora.

Adhesion of microorganisms and subsequent development of surface colonies has been the subject of extensive research5, 6, 7, 8, 9, and 10. Subsequently, several workers collected data on this aspect from the important commercial harbors of India1. Sulphate-reducing bacteria and iron-oxidizing bacteria have long been considered as major contributors of corrosion. Recently, manganese-oxidizers have also been identified as major contributors to corrosion11, 12. Dickinson et al,13 first to identify the deposition of MnO2 as the likely causative agent of corrosion It was found that the ennoblement effect on the stainless steel could be reproduced by coating the coupons with an alternative for the cathodic reduction of MnO2 and such involvement was reported by Linhardt 14
                                                MnO2  +  H2O + e-      ? MnOOH + OH-

                                                MnO2  +  2 H2O + 2e- ? Mn2+  +4 OH-

Considering the importance of MnOB essentially heterotrophic bacteria and its microbial induced corrosion in different material, and lack of information on the genera involved in manganese deposition/oxidation with analyzing the physical properties of sea water were studied. Present study is aimed to identify HB and MHB bacteria in biofilm of various materials exposed to Rameswaram (Latitude 9o 10’ and 9 o 20’ and longitude 79 o 13’   79 o 27’ E) coastal waters (Palk Bay) Southeast coast of India.

PVC coupons (15 cm x 6 cm), Stainless steel coupons (30mm x 15 mm x 2mm), Titanium coupons (15 cm x 3 cm), Brass coupons (15 cm x 10 cm) and Copper coupons (15 cm x 10 cm). All the coupons were polished, washed with detergents and rinsed with distilled water and stored under sterile conditions until use. 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 parameters such as salinity, air and water temperature, hydrogen-ion concentration (pH) and dissolved oxygen. The sea water nutrients were analysed.

Table: 1 shows the average population of Heterotrophic bacterial (HB) and Manganese-oxidizing heterotrophic bacterial (MHB) count in immersed coupons like, PVC, Stainless Steel, Brass, Titanium and Copper. 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 lower population density of Manganese-oxidizing heterotrophic bacteria at Stainless Steel was due to the nature of the surface of the material11. On titanium coupons the count of HB was 3.86 x 105 CFU/cm2 and MHB was 2.86 x105 CFU/cm2, while the counts HB and MHB of copper were recorded as 1.42 x 103 CFU/cm2   and 1.10 x103 CFU/cm2.  Brass coupons recorded the population density of HB and MHB were 4.03 x 106 CFU/cm2 and 2.02 x 106 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. Videla et al.3 reported that the maximum number of bacterial colonization were found in titanium coupons and it served as an ideal substratum for bacterial colonization this may be due to the corrosion resistant nature of the material. The least population density observed in copper coupons could be due to it toxic nature. Ponmariappan et al15 reported less HB population density on copper than Monel in Tuticorn harbour waters. Venugopal et al.16 studied that bacteria and diatoms constitute two major groups of microorganisms that colonize solid surface immersed in Kalppakkam coastal waters. The population density of Manganese-oxidizing heterotrophic bacteria was more or less same as heterotrophic bacteria in all coupons tested. It indicates that most of the heterotrophic bacterial strains isolated were act as manganese depositors after oxidation.

 

Table: 2. Generic composition of heterotrophic bacterial isolates and their present occurrence in immersed coupons like, PVC, Stainless Steel, Brass, Titanium and Copper.

Table: 2 shows the generic composition of heterotrophic bacterial strains isolated from biofilm samples scrapped from various coupons. 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 than Gram-negative on all materials studied. When comparing with other coupons the Brass showed higher population density of Gram-negative group than Gram-positive. The similar findings were reported earlier by Palanichamy et al11. The generic composition and microbial load were found to be varying from material to material. The genera identified under Gram-positive were Bacillus sp., hlococcus sp. and Micrococcus sp. and the Gram-negative strains identified as Pseudomonas sp., Salmonella sp., Vibrio sp. and Proteus sp.  In PVC, the genera identified under Gram-positive included Bacillus sp., Stphylococcus sp. and Micrococcus sp., while the Gram-negative groups were identified as Pseudomonas sp., Salmonella sp., Vibrio sp. and Proteus sp.  In stainless steel coupons, the identified genera of Gram-positive bacteria were Bacillus sp., Staphylococcus sp. and Micrococcus sp., while in Gram-negative group showed all the isolates except Salmonella sp. In brass Gram-negative strains were found to dominate over the Gram-positive by the genre Pseudomonas sp., Salmonella sp., Vibrio sp. and Proteus sp., while Bacillus was the only Gram-positive group on brass. Titanium showed all the Gram-positive isolates like, Bacillus sp., csp. and Micrococcus sp., and all the Gram-negative isolates like. Pseudomonas sp., Salmonella sp, Vibrio sp. and Proteus sp. In copper coupons, the genera identified under Gram-positive included Bacillus sp., and Staphylococcus sp. Micrococcus was not registered from copper. In Gram-negative isolates were identified as Pseudomonas sp., and Vibrio sp., in copper coupons Salmonella sp. and Proteus sp. will absent.

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. all the tested coupons were recorded with both Gram-positive and Gram-negative groups of bacteria. The common contaminant Bacillus sp. was commonly encountered in all the tested materials. Staphylococcus  sp. and Micrococcus sp. were the other Gram-positive isolates from the coupons. Copper coupons did not show the presence of Staphylococcus  sp. The Gram-negative MHB isolates from different coupons contains Pseudomonas sp., E. coli and Vibrio sp. When comparing HB isolates Salmonella sp. and Proteus sp were absent in MHB and E. coli is present. The presence of E. coli registered only from PVC and SS coupons. In general the bacterial strain isolated from all the coupons showed that Gram- positive groups were dominant.

Table: 3. Generic composition of Manganese-oxidizing heterotrophic bacterial isolates and their present occurrence in immersed coupons like, PVC, Stainless Steel, Brass, Titanium and Copper.

The Manganese (Mn) concentration in sea water and biofilm formed in different material were showed in Table: 4. Among the five types of coupons tested PVC exhibited highest Mn value of 5543 ng/g, while lowest Mn value 309 ng/g was recorded from brass coupons. Sea water showed 0.78µg/l concentration of Mn.

Table: 4.Heavy metal concentration in sea water (µg/l) and biofilm (ng/g) on PVC, Stainless Steel, Brass, Titanium and Copper coupons.

Bacterial slim samples generated on the exposed coupons were scrapped using sterile brush and immediately transferred to sterile saline water. All the samples were serially diluted. For quantitative examination of the bacterial colonies, the samples were inoculated by spread plate method. The Zobell Marine Agar medium (2216E) was used to enumerate the heterotrophic bacteria (HB) and K-medium was used to enumerate the Manganese-oxidizing heterotrophic bacteria (MHB). The pure cultures were maintained in slants for bacterial characterization. The isolated bacterial strains were characterized up to generic level was done to the key described in the
Bergey’s manual

of determinative bacteriology
(8thedition and other developed schemes)17. The identification of isolated bacterial strain was done by inoculating each strain in to nutrient broths and nutrient agar plates and incubated for 24-48 hours at 37 oC. The developed cultures were subjected to further microscopic, physiological and biochemical analysis was shown on Table: 6.

Table: 6.Morphology and biochemical characterization of isolated bacterial strains from various materials.

ACKNOWLEDGEMENT: We thank the Co-ordinators, Department of Oceanography and Coastal Area Studies, Alagappa University, Karaikudi, Thondi Campus, Thondi for permission to communicate the results.

References

1.      Nagabhushanam, R., and Sarojini, R., An overview of Indian Research Efforts  on  Marine Wood-boring and Fouling Organisms, (eds  Nagabhushanam, R and  Thompson, M.E.), Fouling organisms of the Indian Ocean Biology and Control Technology, Oxford & IBH publishing Co. Pvt.  Ltd., New Delhi, 1997, pp. 1-79.

2.      Costerton, J. W. and Lewandowski, Z., Annu. Rev. Microbiol., 1995, 49, 711-745.

3.      Videla, H.A. and Characklis W.G., Biofouling and Microbially Influenced Corrosion, Inter. Biodeterioration and Biodegradation, 1992, 29, 195 – 212.

4.      Mitchell, R., and Kirchman, D., The microbial ecology of marine surfaces. In : J.D. Costlow and R.C. Tipper, (eds.) Marine Biodeteriation An Interdisciplinary Study, Naval Institute Press, Annapolis, 1984, pp. 49-56.

5.      Absolom, D.R., Lamberti, F.W., Policova, Z., Zingg, W., Van Oss, D. J., and Neumann, A.W., Surface thermodynamics of bacterial adhesion, Appl. Environ.  Microbio, 1983, 46, 90 – 97.

6.      Barier, R.E., Adhesion in the biologic environment, J. Biomed. Mater.  Res. 1984,12, 123-160.

7.      Barier, R. E., Meyer, A. E., Natiella, R. R., and Carter, J. M., Surface properties determine bioadhesive outcomes: Methods and results, J. Biomed. Mater. Res,1984,18, 337 – 355.

8.      Marshall, K.C., (Ed), Microbias adhesion and aggregation, Dehlem Konferezen Springer Verlag, Berlin, 1984.

9.      Savage, D.C., and Fletcher, M., (eds), Bacterial adhesion, Planum Press, New York, 1985.

10. Hamilton, H. A., Biofilm: Microbial interaction and metabolic activities, In : M. Fletcher, T.R.G. Gray and J.G. Jones (Eds.), Ecology of Microbial Communities,  Society for general microbiology symposium 41, Cambridge University Press, Cambridge, 1987, pp. 361-387.

11. Palanichamy. S., Maruthaumuthu, S., Manickam, S. T., and Rajendran, A., Microfouling of manganese oxidizing bacteria in Tuticorin harbour waters. Curr. Sci, 2002, 82 (7), 865 – 869.

12. Dexter, S. C., and Maruthamuthu, Corrosion, Paper No.01256, 2001, pp. 01256/1-01256/15.

13. Dickinson, W. B., Caccavo, F., and Lewandoski, Z., Corros. Sci. 1996, 38, 1407-1422.

14. Linhardt, P., Abstract paper 011-9, International Society of Electrochemistry, Portugal, 1995.

15. Ponmariappan, S., Kanabiran, S., Stella, C., Mathiarasu, J., and Maruthamuthu, S., Indian. J. Microbiol., 1998, 39, 113-118.

16.  Venugopal, V. P., Rao, T. S., Sargunam, C. A., and Nair, K. V. K., in  Some observations on the biological and biochemical aspects of  biofilm development in Kalpakkam coastal waters.  (eds  Thompson, M. F., Nagabhushanam, R., Sarojini, R., and Fingerman, M.), Recent developments in biofouling control, Oxford and IBH Publishing Co. Pvt. Ltd., New Delhi,1994.

17. Bergeys`s  Manual of Determinative Bacteriology, 8th edn, Warely Press Inc., The Williams and Wilkins Company, Baltimore,1997.

About the Author

Senior Lecturer
Dept. of microbiology
Dr.GRD college of Science,
Civil aerodrome post,
Coimbatore-14

Savage 17HMR Sighting In?

its the 1 with synthetic stock and stainless barrel

just wonderin if i sight it at 100 yards
(91 meters)
how will i go shootin bunnies at 20-50 meters
and roos out to 100 meters
then the occasionall wannabe sniper rabbit shot at 150 meters
will the bullet stay fairly straight

It will no doubt fly flatter in the first 100. I would say do a top of animal or slightly more holdover for those slightly longer shots. There are .17HMR caliber specific scopes that work quite well but will never be perfect. The only true thing is to fire at different ranges and record your clicks, that way you can DOPE (Data Of Previous Engagement) your scope so you are within your ballistic drop requirements.

.17 HMR Performance Test