Abstract.
Pulsed-field gel electrophoresis (PFGE) was applied to analyse sporadic and outbreak cases of cholera caused by V. cholerae O1 biotype El Tor from Vietnam (n=16) and V. cholerae O139 from Malaysia (n=12) and from five vaccine strains. NotI-Digestion of chromosomal DNA from these isolates, followed by PFGE produced eleven different profiles among the 16 V. cholerae O1 isolates (Dice coefficient: 0.67-0.97). The V. cholerae O1 Ogawa and Inaba strains were clearly differentiated into distinct clusters. NotI-PFGE analysis among V. cholerae O139 isolates showed a predominant PFGE profile (N12) indicating that the outbreak was probably derived a single clone. Among the five vaccine strains, the PFGE profiles of V. cholerae Inaba Cairo 48 and classical Inaba Cairo 48 were similar to some of the field isolates of 01 Inaba strains in Vietnam. The PFGE analysis showed that the V. cholerae 0139 isolates from Malaysia were indistinguishable as these strains were probably derived from a cholera outbreak and the V. cholerae O1 isolates from Vietnam exhibited limited genetic diversity.

Key words: PFGE, Vibrio cholerae O1 and O139

^*Author for Correspondence.
Mailing address: Microbiology Division, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia.
Tel No. 603-79674437  Fax No 603-79674606  Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract.
The effects of irradiance and inoculum density on the growth and pigmentation, especially carotenoid composition of Spirulina (Arthospira) platensis UMACC 160 were investigated. The cultures were grown at three irradiance levels (50, 105 and 160 µmol m^-2 s^-1) using two inoculum densities (OD₆₂₀= 0.2 and 2.0). Biomass and pigment contents throughout the growth cycle were determined. The low-density inoculum cultures attained higher specific growth rates (µ) based on dry weight (0.54 day^-1) than the high-density inoculum cultures (0.26 day^-1). For the low-density inoculum cultures, specific growth rate (µ) increased with increasing irradiance. Maximum biomass attained under the various culture conditions reached 1363 mg dry weight L^-1. The contents of phycocyanin, chlorophyll a and carotenoids varied markedly, ranging from 1.1 - 127.0, 7.2 - 32.2 and 3.30 - 12.19 mg g^-1 dry weight respectively. The highest yield of phycocyanin (919 mg L^-1) was attained by the low-density inoculum cultures grown at the lowest irradiance, while the highest yield of carotenoids (8.50 mg L^-1) was attained by the high-density inoculum cultures grown at the highest irradiance, both at stationary phase. The carotenoids consisted of β-carotene (5.50 mg g^-1 dry weight), myxoxanthophyll (4.62 mg g^-1 dry weight), zeaxanthin (2.52 mg g^-1 dry weight) and oscillaxanthin (1.14 mg g^-1 dry weight); the content of each constituent varied with culture age and irradiance, and was dependent on the inoculum density used. Irradiance, inoculum density and culture age are three important factors to be considered for optimisation of pigment production by S. platensis.

Keywords: β-carotene, carotenoids, chlorophyll a, irradiance, phycocyanin, Spirulina platensis

^*Author for Correspondence.
Mailing address: Institute of Biological Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia.
Fax: +603-79568940 Tel: +603-79674610  E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
**Present Address: Micro Gaia, Inc., 535 Lipoa Parkway, Suite 151, Kihei, Maui, Hawaii 96753, USA

Abstract.
Of 42 strains and 65 crude extracts of actinomycetes studied, 12 positive strains and 22 positive extracts were obtained. The strains were isolated from soil/mud samples of mangrove forest, sandbar litter, oil palm plantation and peat soil. Regardless of whether the test strains were neutrophilic or acido-tolerant, Streptomyces spp were noted to be more active against Ganoderma boninense compared to Micromonospora spp. The percentage of Micromonospora strains with bioactivity against G. boninense in primary screening was found to be significantly lower compared to secondary screening, in which crude extracts were prepared and tested. However, the difference between the percentage of positive Streptomycete strains was found to be small and insignificant between the two screenings. Three patterns of fungal mycelial abnormalities were observed in this preliminary study, which suggested production of antibiotic substances by the actinomycete strains to inhibit growth of G. boninense. The results indicated the possibilities of utilizing actinomycetes as biocontrol agent of oil palm basal stem rot.

Keywords: acido-tolerant actinomycetes, antifungal activity, Ganoderma boninense, Micromonospora spp., Streptomyces spp.

^*Author for Correspondence.
Mailing address: Institute of Biological Sciences, Faculty of Science, Universiti Malaya 50603 Kuala Lumpur, Malaysia.
Tel: 603-7967 4349/4425 Fax: 603-7967 4606 E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract.
The regeneration capacity of banana meristem in vitro was compared between single meristem and scalp methods. Scalps were induced on p4 media containing MS (Murashige and Skoog, 1962) components supplemented with coconut water and high concentration of benzyl amino purine (BAP) (75µM). The number of regenerated shoots produced from scalps was six-fold higher than that generated from single meristems. A comparison of the growth response upon gibberelic acid (GA₃) treatment was made between plantlets derived from both methods to detect dwarf off-types. The difference in height and the number of leaves between plantlets from both sources was statistically insignificant. On the other hand, RAPD analysis using 40 random primers displayed approximately 26% variation in single meristem while naked meristem exhibited 74% variation.

Keywords: Micropropagation, somaclonal variation, RAPD analysis, banana, tissue culture

^*Author for Correspondence.
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.