ORCID Profile
0000-0001-7086-9965
Current Organisations
University of Adelaide
,
Primary Industries and Regions SA
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Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.SCITOTENV.2016.10.083
Abstract: Four mercury (Hg) contaminated soils with different pH (7.6, 8.5, 4.2 and 7.02) and total organic carbon contents (2.1, 2.2, 4 and 0.9%) were subjected to bioremediation utilizing a Hg volatilizing bacterial strain Sphingobium SA2 and nutrient amendment. In a field with ~280mg/kgHg, 60% of Hg was removed by bio-augmentation in 7days, and the removal was improved when nutrients were added. Whereas in artificially spiked soils, with ~100mg/kgHg, removal due to bio-augmentation was 33 to 48% in 14days. In the field contaminated soil, nutrient amendment alone without bio-augmentation removed 50% of Hg in 28days. Nutrient amendment also had an impact on Hg remediation in the spiked soils, but the best results were obtained when the strain and nutrients both were applied. The development of longer root lengths from lettuce and cucumber seeds grown in the remediated soils confirmed that the soil quality improved after bioremediation. This study clearly demonstrates the potential of Hg-reducing bacteria in remediation of Hg-contaminated soils. However, it is desirable to trap the volatilized Hg for enhanced bioremediation.
Publisher: Springer Science and Business Media LLC
Date: 27-04-2016
DOI: 10.1007/S11356-016-6696-Z
Abstract: Regulatory assessment of lead (Pb) in contaminated soils is still expressed primarily as total Pb concentrations in soil. In this study, we estimated effective concentrations (ECx) of Pb to Cucumis sativa L. (cucumber) focusing primarily on pore-water Pb data from 10 different soils after 12 weeks ageing. Phytotoxicity expressed in terms of Pb(2+) was observed to occur in the nanomolar range in neutral to alkaline soils (EC50 values 90 to 853 nM) and micromolar levels for acidic soils (EC50 values 7.35 to 9.66 μM). Internal Pb concentrations relating to toxicity (PT50) in roots and shoots also decreased with increasing pore-water pH (R (2) = 0.52 to 0.53). From a series of dose-response studies, we developed transfer functions predicting Pb uptake in C. sativa and we validated these functions with long-term Pb contaminated soils. The significant independent parameters were pore-water Pb(2+) and dissolved Pb plus dissolved organic carbon (DOC). The observed RMSE for the Pb-DOC model and Pb(2+) were 2.6 and 8.8, respectively. The Pb-DOC model tended to under-predict Pb, whilst Pb(2+) tended to over-predict accumulation despite reasonable RMSE values. Further validation is needed in soils with higher pore-water Pb solubility.
Publisher: Elsevier BV
Date: 11-2017
Publisher: Elsevier BV
Date: 08-2020
Publisher: Springer Science and Business Media LLC
Date: 16-05-2022
DOI: 10.1038/S41396-022-01249-0
Abstract: Vibrio cholerae , the bacterial pathogen responsible for the diarrheal disease cholera, resides in the aquatic environment between outbreaks. For bacteria, genetic variation by lateral gene transfer (LGT) is important for survival and adaptation. In the aquatic environment, V. cholerae is predominantly found in biofilms associated with chitinous organisms or with chitin “rain”. Chitin induces competency in V. cholerae , which can lead to LGT. In the environment, V. cholerae is also subjected to predation pressure by protist. Here we investigated whether protozoal predation affected LGT using the integron as a model. Integrons facilitate the integration of mobile DNA (gene cassettes) into the bacterial chromosome. We report that protozoal predation enhances transformation of a gene cassette by as much as 405-fold. We show that oxidative radicals produced in the protozoal phagosome induces the universal SOS response, which in turn upregulates the integron-integrase, the recombinase that facilitates cassette integration. Additionally, we show that during predation, V. cholerae requires the type VI secretion system to acquire the gene cassette from Escherichia coli . These results show that protozoal predation enhances LGT thus producing genetic variants that may have increased capacity to survive grazing. Additionally, the conditions in the food vacuole may make it a “hot spot” for LGT by accumulating erse bacteria and inducing the SOS response helping drive genetic ersification and evolution.
Publisher: Bangladesh Journals Online (JOL)
Date: 1970
Abstract: Antimicrobial properties of chitosan extracted from indigenous shrimp processing waste were determined against one gram-negative (Salmonella Paratyphi) and one gram-positive bacterium (Staphylococcus aureus) in vitro. The antimicrobial activities of chitosan were explored by calculation of the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) in media supplemented with 128, 138, 168, 192, 240, 288, 300 and 320 ppm chitosan solution adjusted to pH 6 or 7. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the prepared chitosan was 288 and 300 ppm for both bacterial strains. These results indicate that chitosan from indigenous shrimp processing waste could be used as an effective antibacterial agent in the food industry. DOI: 0.3329/jbcs.v24i2.9707 Journal of Bangladesh Chemical Society, Vol. 24(2), 185-190, 2011
Publisher: Elsevier BV
Date: 10-2020
Publisher: Springer Science and Business Media LLC
Date: 05-10-2016
DOI: 10.1007/S00128-015-1664-8
Abstract: Three soil types - neutral, alkaline and acidic were experimentally contaminated with nine different concentrations of inorganic mercury (0, 5, 10, 50, 100, 150, 200, 250, 300 mg/kg) to derive effective concentrations of mercury that exert toxicity on soil quality. Bioavailability of mercury in terms of water solubility was lower in acidic soil with higher organic carbon. Dehydrogenase enzyme activity and nitrification rate were chosen as indicators to assess soil quality. Inorganic mercury significantly inhibited (p < 0.001) microbial activities in the soils. The critical mercury contents (EC10) were found to be less than the available safe limits for inorganic mercury which demonstrated inadequacy of existing guideline values.
Publisher: Elsevier BV
Date: 2022
DOI: 10.1016/J.ENVPOL.2021.118506
Abstract: Nanosilver (NAg) is currently one of the major alternative antimicrobials to control microorganisms. With its broad-spectrum efficacy and lucrative commercial values, NAg has been used in medical devices and increasingly, in consumer products and appliances. This widespread use has inevitably led to the release and accumulation of the nanoparticle in water and sediment, in soil and even, wastewater treatment plants (WWTPs). This Article describes the physical and chemical transformations of NAg as well as the impact of the nanoparticle on microbial communities in different environmental settings how the nanoparticle shifts not only the ersity and abundance of microbes, including those that are important in nitrogen cycles and decomposition of organic matters, but also their associated genes and in turn, the key metabolic processes. Current findings on the microbiological activity of the leached soluble silver, solid silver particulates and their respective transformed products, which underpin the mechanism of the nanoparticle toxicity in environmental microbes, is critically discussed. The Article also addresses the emerging evidence of silver-driven co-selection of antibiotic resistance determinants. The mechanism has been linked to the increasing pools of many antibiotic resistance genes already detected in s les from different environmental settings, which could ultimately find their ways to animals and human. The realized ecological impact of NAg calls for more judicial use of the nanoparticle. The generated knowledge can inform strategies for a better 'risks versus benefits' assessment of NAg applications, including the disposal stage.
Publisher: Elsevier BV
Date: 03-2017
Publisher: Elsevier BV
Date: 02-2018
Publisher: Springer Science and Business Media LLC
Date: 22-10-2017
DOI: 10.1007/S11356-016-7869-5
Abstract: Three different soils were spiked with 12 different concentrations of inorganic mercury (Hg). Sub-chronic Hg toxicity tests were carried out with Eisenia fetida in spiked soils by exposing the worms for 28 days following standard procedures. The toxicity studies revealed that Hg exerted less lethal effect on earthworms in acidic soil with higher organic carbon (S-3 soil) where water soluble Hg recovery was very low compared to the water soluble Hg fractions in soils with less organic carbon and higher pH (S-1 and S-2 soils). The concentrations of total Hg that caused 50 % lethality to E. fetida (LC
Publisher: Science Alert
Date: 15-08-2012
Publisher: Bangladesh Journals Online (JOL)
Date: 28-07-2012
DOI: 10.3329/BJSIR.V47I2.11445
Abstract: Growth response of Spirulina platensis in papaya skin extract media and their antimicrobial activity were studied. Five different concentrations e.g. 10gm/L, 8gm/L, 6 gm/L, 4 gm/L and 2gm/L of Papaya (Carica papaya) skin extract media and BD1 (control) medium were used in this study. After 8 days of cultivation, the optical density (0.33) was recorded in BD1 medium and among the five different concentrations of papaya skin extract media the maximum was found (0.31) in 6gm/L. Antimicrobial activity of Spirulina platensis grown in three media namely Zarrouk, BD1 media and media made from papaya skin extract was also studied. Only freeze dried Spirulina platensis powder extract showed inhibitory effect against bacteria and no antifungal activity was observed. DOI: 0.3329/bjsir.v47i2.11445 Bangladesh J. Sci. Ind. Res. 47(2), 147-152, 2012
Publisher: Springer Science and Business Media LLC
Date: 10-01-2017
DOI: 10.1007/S00253-016-8079-2
Abstract: Contamination of land and water caused by heavy metal mercury (Hg) poses a serious threat to biota worldwide. The seriousness of toxicity of this neurotoxin is characterized by its ability to augment in food chains and bind to thiol groups in living tissue. Therefore, different remediation approaches have been implemented to rehabilitate Hg-contaminated sites. Bioremediation is considered as cheaper and greener technology than the conventional physico-chemical means. Large-scale use of Hg-volatilizing bacteria are used to clean up Hg-contaminated waters, but there is no such approach to remediate Hg-contaminated soils. This review focuses on recent uses of Hg-resistant bacteria in bioremediation of mercury-contaminated sites, limitation and advantages of this approach, and identifies the gaps in existing research.
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.CHEMOSPHERE.2015.08.061
Abstract: A mercury resistant bacterial strain, SA2, was isolated from soil contaminated with mercury. The 16S rRNA gene sequence of this isolate showed 99% sequence similarity to the genera Sphingobium and Sphingomonas of α-proteobacteria group. However, the isolate formed a distinct phyletic line with the genus Sphingobium suggesting the strain belongs to Sphingobium sp. Toxicity studies indicated resistance to high levels of mercury with estimated EC50 values 4.5 mg L(-1) and 44.15 mg L(-1) and MIC values 5.1 mg L(-1) and 48.48 mg L(-1) in minimal and rich media, respectively. The strain SA2 was able to volatilize mercury by producing mercuric reductase enzyme which makes it potential candidate for remediating mercury. ICP-QQQ-MS analysis of Hg supplemented culture solutions confirmed that almost 79% mercury in the culture suspension was volatilized in 6 h. A very small amount of mercury was observed to accumulate in cell pellets which was also evident according to ESEM-EDX analysis. The mercuric reductase gene merA was lified and sequenced. The deduced amino acid sequence demonstrated sequence homology with α-proteobacteria and Ascomycota group.
Publisher: Springer Science and Business Media LLC
Date: 27-04-2017
DOI: 10.1007/S00128-017-2096-4
Abstract: In this study, three native Australian grasses namely Iseilema membranaceum (Barcoo), Dichanthium sericeum (Queensland Blue) and Sporobolus africanus (Tussock) were grown in three different soils spiked with different concentrations of inorganic mercury and the root elongation was monitored up to 28 days following the germination. Results showed that mercury at certain concentrations significantly inhibited the root growth of all three tested native grasses grown in three soils, however, the toxicity was less in the soil with high organic carbon content and acidic pH. The calculated EC
Publisher: Bangladesh Journals Online (JOL)
Date: 22-03-2012
Abstract: KR Mahbub added as the First author on 08/08/2012 and corrected PDF loaded on 08/08/2012.The aim of the study was to assess the microbiological quality of Dhaka WASA drinking water. A total of 45 s les were collected from different outlets of WASA water supply chain. Among the these s les 29 s les were collected from house tap, 5 s les from street pipe line tap and 11 s les from WASA source pump. The results of the Total Viable Count (TVC) showed that 62 % s les of house tap water, 60 % pipeline water and 45.45 % WASA pump water were exceeded the BDS standard (1240:2001) and WHO Guideline for drinking. The highest count was 2 × 106 cfu/ml in the house tap water of Gandaria. Total coliform and E. coli count ranged from .8 (MPN) /100 ml to (MPN)/100 ml. Among all the tested s les, 57.78 % water s les were positive for coliform and 51.11 % s les were positive for E. coli bacteria. Out of twenty three E. coli isolates, 8 isolates were subjected to biochemical and microscopic examination for confirmation. All 8 isolates were detected as E. coli based on biochemical parameters. The antibiotic sensitivity pattern of those isolates was determined. Most of them were found resistant to Ampicillin, Amoxicillin, kanamycin, Penicillin, Sulphomethoxazole antibiotics. Nearly all of them were found sensitive to Gentamycin and Nalidixic acid. The s les collected from different house tap water and road side tap water were more contaminated than WASA source pump water. It may therefore be concluded that distribution lines of Dhaka WASA supply chain might be the main source of microbiological contamination of drinking water. In this regard further investigations with more representatively drawn s les are required.DOI: 0.3329/jesnr.v4i2.10133J. Environ. Sci. & Natural Resources, 4(2): 41-49, 2011
Publisher: Elsevier BV
Date: 08-2018
DOI: 10.1016/J.ENVINT.2018.04.037
Abstract: Currently, data that guide safe concentration ranges for inorganic mercury in the soil are lacking and subsequently, threaten soil health. In the present study, a species sensitivity distribution (SSD) approach was applied to estimate critical mercury concentration that has little (HC
Publisher: Springer Science and Business Media LLC
Date: 21-11-2017
DOI: 10.1007/S00253-016-7965-Y
Abstract: This study evaluated the effect of inorganic mercury (Hg) on bacterial community and ersity in different soils. Three soils-neutral, alkaline and acidic-were spiked with six different concentrations of Hg ranging from 0 to 200 mg kg
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 2017
DOI: 10.1016/J.JES.2016.06.032
Abstract: A mercury resistant bacterial strain SE2 was isolated from contaminated soil. The 16s rRNA gene sequencing confirms the strain as Sphingopyxis belongs to the Sphingomonadaceae family of the α-Proteobacteria group. The isolate showed high resistance to mercury with estimated concentrations of Hg that caused 50% reduction in growth (EC
Publisher: Elsevier BV
Date: 08-2021
Publisher: Bangladesh Journals Online (JOL)
Date: 20-12-2010
Abstract: In present study, the occurrence of Salmonella in local chicken eggs and their pattern of antibiotic resistance were determined. 100 egg s les collected from different locations of Dhaka city were analysed and Salmonella spp were found in 8% of the s les. Among all presumptive Salmonella isolates, 8 isolates were confirmed as Salmonella enterica subsp. salamae (4%), Salmonella enterica subsp. indica (1%), Salmonella Paratyphi-A (1%), Salmonella bongori (1%) and Salmonella Choleraesuis (1%) on the basis of serotyping and biochemical analysis. These isolates were subjected to susceptibility test against 10 antibiotic disks. All the isolates were found chlor henicol sensitive. The highest percentage of resistance (87.5%) was found to amoxicillin and icillin. Resistance against erythromycin, cephalexin, doxycycline hydrochloride, ceftazidime, doxycycline and nalidixic acid was also found significant ranging from 25% to 62.5%. Salmonella isolated from egg shell surface were found more antibiotic resistant than that of egg yolk and white. The present study suggests that poultry eggs are potential reservoir of antibiotic resistant Salmonellae.Keywords: Egg Salmonella Characterization Antibiotic resistance.© 2011 JSR Publications. ISSN: 2070-0237 (Print) 2070-0245 (Online). All rights reserved.doi:10.3329/jsr.v3i1.6109 J. Sci. Res. 3 (1), 191-196 (2011)
Publisher: Bangladesh Journals Online (JOL)
Date: 24-04-2014
Abstract: The present study was aimed to assess the microbiological quality of street vended drinking water of Dhaka city. The water s les were collected from street vendors in different areas of Dhaka city. All of the 30 s les were found having microorganisms higher than WHO limits for drinking water. Four (13.34%) s les were confirmed to have Salmonella contamination and twenty (66.67%) s les were contaminated with Pseudomonas. Based on morphological and biochemical characterization Salmonella isolates were identified as Salmonella choleraesuis and Salmonella bongori. Among the isolates of Pseudomonas, fourteen were identified as Pseudomonas alcaligens and six were as Pseudomonas aeruginosa. During antibiogram for Salmonella, 100% of the isolates were found resistant to Penicillin. Chlor henicol, doxycycline, Gentamycin, Neomycin were sensitive to all of the isolates. The Pseudomonas isolates showed a significant drug resistance to Penicillin (100%), Ampicillin (95%), Amoxicillin (95%) and Nalidixic acid (85%). The present study demonstrates that drinking water s les from street vendors in Dhaka city are not complying with microbiological specifications of WHO and indicates that street vending drinking water in Dhaka city may not be safe for human consumption and also shows that these are the potential sources of drug resistance Salmonella and Pseudomonas. Keywords: Street vended drinking water Antibiotic resistance Salmonella Pseudomonas. © 2014 JSR Publications. ISSN: 2070-0237 (Print) 2070-0245 (Online). All rights reserved. doi: 0.3329/jsr.v6i2.17640 J. Sci. Res. 6 (2), 359-371 (2014)
Publisher: Elsevier BV
Date: 10-2020
Location: Bangladesh
No related grants have been discovered for Khandaker Mahbub.