Title

Sulfonate metabolism by some aerobic and anaerobic bacteria

Date of Completion

January 2004

Keywords

Biology, Microbiology

Degree

Ph.D.

Abstract

The ability of various Rhodococcus spp., aerobes, to use some short-chain 1-alkanesulfonates as a sole sulfur source for growth has been established. The intracytoplasmic inclusions formed by Rhodococcus opacus TCNS94 and Arthrobacter crystallopoietes were shown to consist of triacylglycerols. The poly-β-hydroxybutyrate inclusions and spinae of Desulforhopalus singaporensis, a sulfate-reducing bacterium, were examined by transmission electron microscopy. ^ Some enzymological aspects of taurine utilization in diverse bacteria were investigated. The bacteria included Rhodococcus spp., Arthrobacter crystallopoietes, and the anaerobe, Desulforhopalus singaporensis. When these bacteria were grown with taurine, aminotransferase and sulfoacetaldehyde acetyltransferase activities were induced to degrade this compound. Unique polypeptides in the soluble fraction (∼41–42, 49–51, and 63–64 kDa) were induced during taurine utilization. ^ Desulfobacterium autotrophicum, a sulfate-reducing bacterium, could grow with cysteate as carbon and energy source and terminal oxidant; the end products were sulfide, ammonia, and some acetate. Constitutive aminotransferase was concluded to be responsible for the initial cysteate catabolism in Desulfobacterium autotrophicum and Desulfovibrio desulfuricans strain ICI, another sulfate-reducing bacterium. APS reductase activity was found to be constitutive in Desulfobacterium autotrophicum, although the specific activity for this enzyme varied with different growth substrates. Similar molecular weight polypeptides (∼34 and 32 kDa, respectively) were induced in Desulfobacterium autotrophicum, Desulfovibrio desulfuricans strain IC1, and another sulfate-reducing bacterium, Desulfomicrobium norvegicum when cysteate was a growth substrate. ^ The physiological characteristics of two other strains of sulfate-reducing bacteria, TP1 and Wood, were examined. These bacteria were able to grow with lactate and isethionate; isethionate was the only sulfonate that could serve as terminal oxidant. The specific activity of APS reductase was much lower in these bacteria when grown with lactate + isethionate compared to growth with lactate + sulfate. Additionally, a ∼90 kDa polypeptide was induced in both of these bacteria when grown with lactate + isethionate. ^ While diverse bacteria were shown to have similar methods for catabolizing the same sulfonate, taurine, the pathways for cysteate or isethionate metabolism by sulfate-reducing bacteria remain unknown. The different molecular weight polypeptides induced in these bacteria suggests that unique enzymes are probably involved in the metabolism of cysteate and isethionate by sulfate-reducing bacteria. ^