Lolo Wal Marzan

Metabolic regulation of an fnr gene knockout Escherichia coli under oxygen limitation

The effect of fnr gene knockout on the metabolism of Escherchia coli was investigated under microaerobic condition based on gene expressions, enzyme activities, and intracellular metabolic fluxes. Under micro-aerobic condition, the flux through Pfl and Frd were reduced for the mutant, and the decreased flux through Pfl may have caused accumulation of PYR, which increased the flux through LDH. The fnr gene knockout caused arcA to be down-regulated, and thus the TCA cycle was activated, and cyoA and cydB genes were up-regulated. The down-regulation of arcA caused lpdA to be up-regulated where the flux through PDHc increased. The fnr gene knockout indirectly affected cra gene transcript level to be decreased, which in turn caused the glycolysis genes to be up-regulated, which corresponded to the increase in the specific glucose consumption rate. The fnr gene knockout also caused crp transcript level to be increased, where there might be some relationship between the two due to similar structure and gene sequence.

Optimization of some fermentation conditions for the production of extracellular amylases by using Chryseobacterium and Bacillus isolates from organic kitchen wastes

Amylolytic bacterial isolates were obtained by starch-agar plate method from municipal solid wastes. Six amylolytic bacteria were isolated and the best two isolates, named as DY and W1, were selected based on clear zone ratio. The 16S rDNA sequence analysis identified DY and W1 isolates as Chryseobacterium sp. and Bacillus sp., respectively. Amylase production was optimized using basal media. The maximum level of amylase production was achieved from Chryseobacterium and Bacillus isolates after 60 h and 48 h of cultivation, respectively. The optimal temperature, initial pH of the media, agitation and inoculum size were determined for the both isolates. Increased amylase production was observed when basal media were substituted with organic carbon and nitrogen sources. The optimum pH and temperature for amylase activity of the crude amylase of Chryseobacterium sp. were 5.0 and 50 °C, respectively and those of amylase from Bacillus sp. were pH 7.0 and 50 °C, correspondingly. The crude amylase from the Chryseobacterium sp. was stable at pH 5.0–6.0 and up to 40 °C but that from Bacillus sp. was stable at pH 7.0 and up to 30 °C. Amylases from both the isolates lost ∼50% activity when stored at room temperature for two days. Under the optimized fermentation conditions both Chryseobacterium and Bacillus isolates produced almost the similar amount of amylase with organic kitchen wastes compared to the basal media. Results reported herein support the notion that Chryseobacterium sp. and Bacillus sp. can be used to produce industrially important amylases by utilizing organic kitchen wastes.

A single metabolite production by Escherichia coli BW25113 and its pflA.cra mutant cultivated under microaerobic conditions using glycerol or glucose as a carbon source

Abundant, low prices and a highly reduced nature make glycerol to be an ideal feedstock for the production of reduced biochemicals and biofuels. Escherichia coli has been paid much attention as the platform of microbial cell factories due to its high growth rate (giving higher metabolite production rate) and the capability of utilizing a wide range of carbon sources. However, one of the drawbacks of using E. coli as a platform is its mixed metabolite formation under anaerobic conditions. In the present study, it was shown that ethanol could be exclusively produced from glycerol by the wild type E. coli, while d-lactic acid could be exclusively produced from glucose by pflA.cra mutant, where the glucose uptake rate could be increased by this mutant as compared to the wild type strain. It was also shown that the growth rate is significantly reduced in pflA.cra mutant for the case of using glycerol as a carbon source due to redox imbalance. The metabolic regulation mechanisms behind the fermentation characteristic were clarified to some extent.

First genotype characterization of Giardia intestinalis Assemblage E from goat kids in Bangladesh.

Giardiasis is an important protozoan disease caused by Giardia and manifested as life-threatening diarrhea in animals and humans worldwide. No study has performed to see zoonotic epidemiology and diversity of Giardia in animals in Bangladesh. Hence, there is a room to characterize Giardia protozoan parasite in animals to find out their roles as a source of human infection. To address this hurdle, fecal samples of 100 goat kids were genotyped by nested PCR amplification of β-giardin gene fragment followed by sequencing and analysis. The total prevalence of Giardia in goat kids was 3% (3/100) and the infection is more widespread in younger, Black Bengal breed and female goat kids. Further analysis of β-giardin gene locus has shown and clustered the Giardia in Assemblage E rather than Assemblages A and B. It suggests the low zoonotic transmission frequency from the goat kids and has least epidemiological significance to humans. Further study on this field is prerequisite in terms of broad geographical areas, age groups, sex and evaluates zoonotic significance along with genetic diversity in other host species as well.

Characterization of furnace oil bioremediation potential of hydrocarbonoclastic bacteria isolated from petroleum contaminated sites of the Sundarbans, Bangladesh

Spillage of furnace oil is a more frequent event in recent times. In this study, environmental samples from furnace oil spillage sites of the Shela River, the Sundarbans, Bangladesh, were collected after three weeks of spillage. Serial dilution was applied and total seven bacterial isolates were separated as pure cultures. The oil-degrading potentiality of all seven isolates was further assessed, confirmed and compared with the growth pattern in furnace oil supplemented media, 2, 6-dichlorophenolindophenol test, and gravimetric analysis. After 7 days of incubation, isolates SS3, RW2, and SB degraded 56%, 43%, and 52% of supplemented furnace oil, respectively. The top three hydrocarbonoclastic bacterial isolates were selected as potential and identified as Pseudomonas aeruginosa (SS3), Bacillus sp. (RW2), and Serratia sp. (SB). All three isolates showed significant oil-degrading capacity compared to negative control, when incubated in sterile pond water supplemented with 2% furnace oil, suggesting them as potential bioremediation agents.

Molecular characterization of Giardia intestinalis assemblage E from goat kids in Bangladesh

Abstract Objective To molecularly characterize Giardia in goat kids to elucidate the possible zoonotic hazards in Bangladesh and find out the role of Giardia protozoan parasite as a source of human infection. Methods Fecal samples of 100 goat kids were genotyped by nested PCR amplification of β-giardin gene fragment followed by sequencing and analysis. Results The total prevalence of Giardia in goat kids was 3% (3/100) and the infection is more widespread in younger ( P = 0.36), Black Bengal breed ( P = 0.81) and female goat kids ( P = 0.58). Further analysis of β - giardin gene locus has shown that the gene clustered in assemblage E rather than assemblages A and B. Conclusions The present study suggests the low zoonotic transmission frequency from the goat kids and and giardiasis has least epidemiological significance to humans. Further study on this field is prerequisite in terms of broad geographical areas, age groups, sex and evaluation of zoonotic significance along with genetic diversity in other host species as well.