1.Characterization and antimicrobial activities of two Streptomyces isolates from soil in the periphery of Universiti Putra Malaysia
Nurul Zarith Mohamad Zin ; Nor Asmara Tasrip ; Mohd Nasir Mohd Desa,* ; Cheah Yoke Kqueen ; Zainul Amiruddin Zakaria ; Rukman Awang Hamat ; Mariana Nor Shamsudin,
Tropical Biomedicine 2011;28(3):651-660
This study was to assess the identification and antimicrobial activities of two
actinomycete isolates. The two isolates designated as B8 and C2, were isolated from a patch
of soil in the peripheral area of Universiti Putra Malaysia by streaking on starch casein agar
after standard serial dilution procedures. Their antimicrobial activities were first evaluated
against eight clinical laboratory strains namely Bacillus sp., Enterococcus sp., Escherichia
coli, Klebsiella sp., Pseudomonas sp., Salmonella sp., Staphylococcus aureus, and
Staphylococcus epidermidis by perpendicular streak method on Mueller Hinton and Tryptic
Soy agar. In both media, a broad-spectrum antibacterial activity was observed for both
isolates, with B8 against all the test bacteria and C2 against five of them (Bacillus sp., E. coli,
Pseudomonas sp., S. aureus and S. epidermidis). Re-assessment against E. coli ATCC 25922
and S. aureus ATCC 25923 strains by similar method showed antibacterial activities by
isolate B8 against both ATTC strains while C2 only against S. aureus ATCC 25923. Streptomyces
griseus ATCC 10137 was included in the later experiment and showed antibacterial activity
against both ATCC strains. Subsequently, the two isolates were identified by PCR/sequencing
techniques and phylogenetic analysis to be Streptomyces species (>93% homology based on
16S rRNA and rpoB genes). Characterization on cultural characteristic and viable count at
different temperatures (37ºC and 28ºC), on different microbiological media (AIA, ISP-2, MHA,
NA, PDA and TSA), were performed. More morphological features were observed on ISP-2 for
both isolates. A higher growth yield was also observed at 28ºC in all media but in comparing
that between the two isolates, isolate B8 outnumbered C2 at all experimental conditions. The
observed variation in cultural traits and growth yield indicate unique properties between the
two antibiotic-producing isolates