A. R. Omar^1* and K. A. Schat

^*1Department of Veterinary Pathology and Microbiology, Faculty of Veterinary Medicine and Animal Science, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia, Department of Microbiology and Immunology,
College of Veterinary Medicine, Cornell University, Ithaca, NY 14850, USA.

(Received 8 December 1997 / Accepted 10 January 1998)

Abstract.
Marek's disease virus (MDV) genes with homology to herpes simplex virus genes encoding for immediate early, early and late proteins and genes unique to MDV have been cloned and sequenced. Similarly, MDV genes that have significant homology to known oncogenes have also been characterized. Chickens vaccinated against this disease induce neutralizing antibody response and probably cytotoxic T lymphocyte activity that confer protection against subsequent challenge.

Keywords: Molecular Biology, Immunology, Marek's Disease Virus

Aris Tri Wahyudi, Antonius Suwanto*, Tedja Imas and Aris Tjahjoleksono

Department of Biology, Faculty of Mathematics and Sciences, Bogor Agricultural University, Jl. Raya Pajajaran, Bogor 16144, Indonesia.

(Received 9 August 1997 / Accepted 18 November 1997)

Abstract.
The genes, inaZ from Pseudomonas syringae, xylE from P. putida and the kanamycin resistance gene (Km^R) of mini-Tn5Km1, were studied for their capabilities and reliabilities as molecular markers in three acid tolerant Bradyrliizobium japonicum strains. Conjugation was used to transfer each of these genes to B. japonicum strains. Mating was conducted on membrane filter (0.45 gm, Millipore) using modified Luria Agar. The results showed that all of the genes were able to be transferred to acid tolerant B. japonicum strains by conjugation. All of these bacteria were able to express the inaZ and Km^R genes. However, none of the exconjugants was able to express the xylE gene. Acid tolerant B. japonicum strains that carried each of these genes were able to form root nodules in either siratro or soybean plant. The KmR gene had high stability as tested after nodulation. experiments. This gene was subsequently used as a genetic marker in a competition study of acid tolerant B. japonicum strains for nodule occupancy in soybean plant. This study was conducted using acid tolerant soybean cultivar (B 09) grown in Leonard jars using nitrogen free nutrient solution (pH 4.5 + Al 50 µM). Mixtures of acid tolerant B. japonicum strains and USDA 110 were inoculated in 1:1 ratio and nodules were harvested 30 days after planting. The results indicated that one exconjugant strain (11.71Km) dominated root nodules. Thus this strain has the potential to be developed as soybean inoculant in acid soils.

Keywords: Acid Aluminium Tolerance, Bradyrhizobium japonicum Marker Genes, Competition

Saovaros Svasti¹, Wipa Chungjatupornchaj² and Sakol Panyim ^I,2,*

¹Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
²Institute of Science and Technology for Research and Development, Mahidol University, Salaya Campus,
Nakornpathom, 73170, Thailand.

(Received 22 September 1997 / Accepted 9 February 1998)

Abstract.
Expression of giant catfish growth hormone (gcGH) gene under the control of the lambda Pr promoter was comparatively low in Escherichia coli. mRNA secondary structure analysis predicted that there are new two hairpin loops: one at the Shine Dalgarno (SD) sequence region with ?G = 7.9 kcal/mol, the other at the initiation codon region with ?G = 4.2 kcal/mol. The effect of the mRNA secondary structures on the expression level of gcGH gene in E. coli was investigated. Several site specific mutations were introduced into stem loops at the Shine Dalgarno (SD) sequence region and the initiation codon region to disrupt the secondary structures. Completely destabilizing the stem loop at the SD sequence region while maintaining that at the initiation codon region, or vice versa, increased gcGH gene expression level fifty five and fifty folds, respectively. Complete destabilization of the two stem loops hence creating a new stem loop increased the gcGH expression one hundred and five fold.

Keywords: Growth Hormone, Giant Catfish, mRNA

M.S. Madihah, A.B. Ariff*, F.H. Akmam¹, A.G. Baharuddin¹ and MIA Karim

Department of Biotechnology, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia; 1Land & General Berhad, No 7, Persiaran Dagang, Bandar Sri Damansara, 52200 Kuala Lumpur, Malaysia.

(Received 9 September 1997 / Accepted 18 November 1997)

Abstract.
Production waters, collected from 9 petroleum reservoirs in Malaysia, were examined chemically and microbiologically to investigate the potential for microbiological enhanced oil recovery. For all petroleum reservoirs investigated, surface water is injected into the reservoirs as part of the secondary oil recovery processes. The depth, temperature, salinity and pH of the reservoirs ranged from 697 to 2,412 metres, 35^oC to 94.5^oC, 29,250 mg/I to 126,500 mg/I and 6.36 to 8.41, respectively. Chemical analysis indicated a lack of soluble nitrogen and phosphorus in all production waters. However, the waters from all reservoirs are rich with metal ions. The partially characterized strains isolated from the reservoirs were assigned to three morphologically distinctive groups (i) pleomorphic rodshaped which appeared singly or in pairs, (ii) sheathed rod shaped bacteria with single terminal spheroids, and (iii) non sheathed rod shaped with terminal sporulation. These bacteria grew well around neutral pH and temperatures ranging from 60^oC to 90^oC. Growth of all bacteria was supported individually by yeast extract. The bacteria also grew well in fermentable carbon sources such as glucose, mannose and lactate with significant production of ethanol, acetone, organic acids (oxalic, tartaric, malic, acetic and succinic), C0₂ and H₂' suggesting that the bacteria were fermentative.

Keywords: Extreme Thermophile, Anaerobic Bacteria, Fermentative Bacteria, Petroleum Reservoirs.