Intact cells of Thiobacillus ferrooxidans NASF-1 incubated under anaerobic conditions in a reaction mixture containing 0.5% colloidal sulfur produced hydrogen sulfide (H2S) extracellularly. The amount of H2S produced by cells increased corresponding to the cell amounts and colloidal sulfur. Two activity peaks of H2S production were observed at pH 1.5 and 7.5. We tentatively called the enzyme activities pH 1.5- and pH 7.5-sulfur reducing systems, respectively. Seven strains of T. ferrooxidans tested had both the activities of pH 1.5- and pH 7.5-sulfur reducing systems, but at different levels. T. ferrooxidans NASF-1 showed the highest activity of the pH 1.5-sulfur reducing system and strain 13598 from ATCC showed the highest activity of the pH 7.5-sulfur reducing system. Further characteristics of H2S production were studied with intact cells of NASF-1. The optimum temperatures for pH 1.5- and pH 7.5-sulfur reducing systems of NASF-1 were 40°C. Hydrogen sulfide production continued for 8 days and total amounts of H2S produced at pH 7.5 and 1.5 were 832 and 620 nmol/mg protein, respectively. The pH 7.5-sulfur reducing system used only colloidal sulfur as the electron acceptor. However, the pH 1.5-sulfur reducing system used both colloidal sulfur and tetrathionate. Thiosulfate, dithionate, and sulfite could not be used as the electron acceptor for both of the sulfur reducing systems. Potassium cyanide activated by 3- fold the pH 1.5-sulfur reducing system activity at 0.5 mM but did not affect the activity of the pH 7.5-sulfur reducing system. An inhibitor of sulfite reductase, p-chloromercuribenzene sulfonic acid, did not affect either enzyme activity. Sodium molybdate and monoiodoacetic acid strongly inhibited the activity of the pH 1.5-sulfur reducing system at 1.0 mM, but not the activity of pH 7.5-sulfur reducing system.
A few members of a widespread class of bacterial and archaeal flavo-diiron proteins, dubbed FprAs, have been shown to function as either oxidases (dioxygen reductases) or scavenging nitric oxide reductases, but the questions of which of these functions dominates in vivo for a given FprA and whether all FprAs function as oxidases or nitric oxide reductases remain to be clarified. To address these questions, an FprA has been characterized from the anaerobic sulfate-reducing bacterium Desulfovibrio vulgaris. The gene encoding this D. vulgaris FprA lies downstream of an operon encoding superoxide reductase and rubredoxin, consistent with an O2-scavenging oxidase function for this FprA. The recombinant D. vulgaris FprA can indeed serve as the terminal component of an NADH oxidase. However, this oxidase turnover results in irreversible inactivation of the enzyme. On the other hand, the recombinant D. vulgaris FprA shows robust anaerobic nitric oxide reductase activity in vitro and also protects a nitric oxide-sensitive Escherichia coli strain against exposure to exogenous nitric oxide. It is, therefore, proposed that this D. vulgaris FprA functions as a scavenging nitric oxide reductase in vivo and that this activity protects D. vulgaris against anaerobic exposure to nitric oxide. The location of a gene encoding a second FprA homologue in the D. vulgaris genome also suggests its involvement in nitrogen oxide metabolism.
A strain of At. ferrooxidans was isolated from Penjom Goldmine, Kuala Lipis, Pahang, Malaysia. The 16S rRNA partial gene sequence analysis revealed that this rod-shaped bacterium with size of 0.3 x 0.8 -m is a strain of At. ferrooxidans, and was designated as At. ferrooxidans KLipis-3-1. The whole-cell FAMEs profile analysis showed that At. ferrooxidans KLipis-3-1 possesses large amounts of C18:1, C16:0 and C16:1 fatty acids with C18:1 as the predominant fatty acid. The initial specific iron-oxidizing and molybdenum blue-oxidizing activities of this bacterium were 88.85 mMh-1mg-1 and 196.86 mMh-1mg-1, respectively, which were similar to the activities observed in the type strain At. ferrooxidans ATCC 23270. However, At. ferrooxidans KLipis-3-1 has a higher resistance towards Mo6+ at concentration above 1 mM. At. ferrooxidans KLipis-3-1 has the ability to reduce ferric ion with elemental sulfur as electron donor, with the initial specific SFORase activity of 0.47 mMh-1mg-1. The bioleaching capability of At. ferrooxidans KLipis-3-1 and At. ferrooxidans ATCC 23270 with pyrite as substrate at selected parameters operated in a batch bioprocess were studied.
Tujuan kajian bagi projek penyelidikan ini ialah untuk melihat peranan dan usaha PKENJ dalam bidang pertanian dan meninjau corak sosio ekonomi pekerja ladang di ladang milik PKENJ. Kajian luar untuk projek penyelidikan ini telah dijalankan d1 Ladang baru,iaitu salah sebuah ladang milik PKENJ. Di dalam Bab I, pengkaji telah menghuraikan tujuan, metode dan masalah yang dihadapi semasa menjalankan projek penyelidikan ini. Bab II pula membincangkan kegiatan PKENJ dengan pemmpuan kepada kegiatannya dalam memajukan pertanian di negeri Johor. Bab III dan IV pula menerangkan tentang keadaan sosial ekonomi pekerja dan keadaan kerja, serta hubungannya dengan Kesatuan kerja. Akhir sekali, dalam Bab IV, pengkaji telah merumuskan segala penemuan-penemuan kajian ini.
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