Thiobacillus intermedius Marina Richard Generalities about the Thiobacillus Genus1, 2, 3, 4
The genus Thiobacillus consists of a colorless gram negative bacteria. They are rod shaped and move using a polar flagella. Cells are 0.3 x 1 to 3?m in size and are non-spore forming. The bacterium best grows at 25 to 35oC and pH range of 3 to 7. It features the ability to gain energy from the oxidation of elemental sulfur and sulfur containing compounds. Thiobacilli are obligate autotrophs, they cannot grow with organic carbon as an electron and carbon source. T. intermedius is dependant on S2O32- for its growth. A few species can sometimes assimilate a small number of organic compounds but only to a limited extent and in a restricted pattern. T. intermedius is one of these facultative chemolithotrophs that can grow with an organic electron donor. Other inorganic source of energy for some members of this group include hydrogen, ferrous iron, and other reduced metal ions. All species of Thiobacillus are respiratory, being able to use oxygen as their terminal electron acceptor.
Steps in the oxidation of different compounds by Thiobacilli (Ref. 7)
Within certain limits (i.e., NaCl requirement), the Thiobacilli probably have similar requirements for inorganic salts. All of the known species can be cultivated in chemically defined media. However many of their nutritional needs have not been quantitatively established, and the chemical composition of the basal media used in different laboratories varies enormously.
In nature, the distribution of reduced inorganic sulfur compounds is only one of the factor governing the presence and activity of the colorless sulfur bacteria. One crucial factor is the requirement for the simultaneous presence of an electron donor and electron acceptor (i.e., oxygen or nitrogen oxides). The bacteria tends to grow in narrow zones and gradients where sulfide and oxygen coexist, such as in stratified lakes and at the interface between aerobic water and anaerobic sediment. There are two main type of Thiobacillus, one that grows only in neutral pH and the other (including T. intermedius) that are the species that grow in environment that are not neutral pHs. Marine and fresh water strains are known
Thiobacillus implications for the environment1, 2, 3, 4:
Because many of the colorless sulfur bacteria produce sulfuric acid, they are often associated with the oxidative corrosion of concrete and pipes, and have been implicated in the corrosion of buildings and ancient monuments. Acid and metal pollution can also be a result of the activity of Thiobacilli in mine waste (Tuovinen and Kelly, 1972). On the more positive side, the production of acid can be used in leaching process for the extraction of metals from poor ores that are unsuitable for extraction by conventional metallurgical methods.
In soils, Thiobacilli may sometimes be responsible for the solubilization of sulfur compounds, thus making sulfur available (as sulfate) for assimilation by other microorganisms and plants.
Thiobacillus intermedius culture and growth4
Autotrophic growth for T. intermedius is slow, and mixtures of glucose and thiosulfate give a much faster growth rate. While able to grow heterotrophically, it requires a reduced sulfur compound as a source of sulfur. Thiosulfate can be replaced by yeast extract or by a mixture of thiamine pyrophosphate, reduced glutathione, lipoic acid, methionine, cysteine (each at final concentration of 0.15mM) together with biotin and coezyme A (end concentration 0.015mM) (Smith and Rittenberg, 1974). Although many Thiobacilli will grow in media designed for T. intermedius, the enrichment of this species may be promoted if the pH is allowed to fall below 4.0 as it is relatively acid tolerant. In addition to NH4+ and NO3-, organic nitrogen compounds can be used as a source of nitrogen.
According to a recent research5, 6 T. intermedius has been indentified as being able to resist heavy metal when introduced in their environment. The T. intermedius growth was compared to the Escherichia coli and Agrobacterium radiobacter It was observed that aluminum, iron and lead produced no growth inhibition zone for the three bacteria. On a short term-high level experiment, the T. intermedius growth was slightly retarded in the presence of nickel and zinc which strongly inhibited cell growth of E. coli and A. radiobacter. Cadmium was determined to be the most toxic heavy metal and the strongest inhibitor for the three strains. In summary, the result show that the three bacteria were resistant to aluminum and lead, but not to cadmium, zinc and nickel. Although T. intermedius had resistance to zinc and nickel, it was more sensitive to molybdenum than the two other strains. Thiobacillus studies on the relationship between bacteria and heavy metal reveal the existence of a highly specific resistance system to the toxic exposure of heavy metals.
4. Balows, A.: The Prokaryotes : a handbook on the biology of bacteria : ecophysiology, isolation, identification, applications, New York Springer-Verlag, (1992)
5. Yoshida, N., Morinaga, T., and Murroka, Y.: Characterization and indentification of bacterials strains isolated from corroded concrete in the accumulation stratum and their resistance levels to heavy metals, J. Ferment. Bioeng., 76, 400-402 (1993)
6. Yoshida, N., Murroka, Y., Ogawa, K.: Heavy metal particle resitance in Thiobacillus Intermedius 13-1 isolated from corroded concrete, J. Ferment. Bioeng., 85, 630-633 (1998)
7. Madigan, M., Martinko, J., Parker, J.: Biology of microorganisms Brock, 8th ed., 661-663 (1997)
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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