Horizontal gene transfer among nitrogen-fixing bacteria in the guts of termite Coptotermes gestroi

Aims@#Arthropods guts, such as termite harbor diverse microorganisms including those that are capable of fixing atmospheric nitrogen (N2). Nitrogen-fixing bacteria can help termite to overcome their shortage of dietary N by providing fixed N2. Nitrogenase enzyme is responsible for this trait and encoded by nif genes which are highly conserved and are primarily used in the identification of N2-fixing microorganisms. Here, we characterized N2-fixing bacteria isolated from the hindguts of termite Coptotermes gestroi.@*Methodology and results@#A total of 46 bacterial isolates were obtained after a primary screening based on their ability to grow on Burk’s media. Subsequently, the nifH gene from two of these isolates, namely S7 and S20, were successfully amplified and sequenced. Molecular phylogenetic analysis of 16S rRNA gene sequence revealed that isolate S7 is closely related to Ralstonia pickettii ATCC27511 (99.34% similarity, 1059 bp), whereas isolate S20 is closely related to Microbacterium sp. NCCP-451 (LC488936) (99.06% similarity, 948 bp). Besides that, the recA gene of isolate S7 is closely related to Ralstonia pickettii 12D (CP001644) (100% similarity, 442 bp) and the type strain of Ralstonia pickettii (ATCC 27511) (NZ KN050646) (98.97% similarity, 438 bp). Meanwhile, nifH gene of isolate S7 showed highest similarity to the uncultured bacterium NR1606 (AF035490) (99.93% similarity, 277 bp). Moreover, the nifH gene of isolate S20 is clearly separated from Azoarcus sp. and distantly related to Microbacterium sp. The incongruence between the partial 16S rRNA and nifH gene sequences could indicate the possibility of horizontal transfer of nif genes.@*Conclusion, significance and impact of study@#The phylogenetic incongruence between housekeeping genes (16S rRNA and RecA) and nifH gene in these bacteria provides new insight on potential horizontal gene transfer (HGT) activity taking place in bacterial communities particularly in the guts of arthropods. The finding of this study on potential HGT can also aid in the prediction of origins and evolution of gene transfer among bacteria.

Prevalence of antibiotic resistant bacteria isolated from raw chicken meat

Aims@#Antibiotics are widely used in poultry industry for treatment, control and in preventing the spread of infectious diseases among chicken flocks. The uncontrolled use of antibiotic causes the emergence of antibiotic resistant bacteria which is a major concern worldwide. The aim of this study is to isolate and molecularly identify antibiotic resistant bacteria using raw chicken meat samples from farm, supermarket, wet market as well as free-range chicken. @*Methodology and results@#A total of 34 isolates were obtained through primary screening based on their ability to grow on streptomycin, kanamycin, ampicillin and cefazolin antibiotic plates. Kirby-Bauer disc diffusion test performed on the 34 isolates showed that they were highly resistant to oxacillin (97%) and penicillin (94%) followed by ampicillin (64%), cefazolin (50%), tetracycline (32%), erythromycin (24%), ciprofloxacin (21%) and least resistance towards gentamycin (6%). Eight isolates with the highest antibiotic resistance, were selected for molecular identification using 16S rDNA sequencing. Analysis of the 16S rDNA sequence using BLASTN and phylogenetic tree constructed on the selected isolates revealed that five different species of antibiotic resistant bacteria namely Escherichia coli, Klebsiella sp., Chryseobacterium gleum, Comamonas testosteroni and Bacillus cereus were successfully identified from the different types of chicken sample.@*Conclusion, significance and impact of study@#The excessive use of antibiotic in the poultry farm industries had caused the emergence of antibiotic resistant bacteria which can harm the health of people consuming chicken meat. To overcome this crisis, antibiotic usage in the poultry farm industries should be regulated.