This journal is a peer reviewed scientific forum for the latest advancements in bacteriology research on a wide range of topics including food safety, food microbiology, gut microbiology, biofuels, bioremediation, environmental microbiology, fermentation, probiotics, and veterinary microbiology. Because of our open access digital publication model, we believe that Agriculture, Food and Analytical Bacteriology will have a major and immediate impact on advancing scientific research that will only increase as the journal grows.

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AFAB Journal - Volume 4 Issue 3

Volume 4 Issue 3

Published September 2014

Articles in this issue

  • The Prevalence of E. coli O157:H7 in the Production of Organic Herbs and a Case Study of Organic Lemongrass Intended for Use in Blended Tea

    Published 10/2014

    Volume 4 Issue 3
    Pp. 164-176

    Keywords: , , , ,

    Abstract:

    Tea blended with different herbs bring a world of flavors, aromas and colors and is usually made with dried tea leaves, or blended with other dried herbs and involves pouring boiling water over the leaves, letting them steep for few minutes followed by consumption. This study was done to evaluate the insights of potential microbial contamination of organic herbs production at the farm, after harvest, washing, before or after drying and packaging of dried herbs sample. Organic compost, water quality, worker hygiene status and overall food safety management systems were also evaluated to identify additional factors affecting microbiological contamination. In addition, effect of pouring hot water over contaminated dried leaves in a cup of tea was observed. The study was designed in such a way that reflects the actual tea preparation at home. Presence of higher numbers of generic E. coli and pathogenic E. coli O157:H7 was observed in dried tea, herbs and /or lemongrass samples, and blended tea mix lemongrass samples. However, no Salmonella was detected in any of the samples tested. When hot water was added into dried lemongrass or blended tea mix lemongrass samples in a cup of tea and held for 30, 60, 90, 120 or 180 seconds with or without a lid, no generic E. coli and pathogenic E. coli O157:H7 was observed in the prepared cup of tea in 30 seconds or above the holding time in selective medium. The bacteria might be severely injured by hot water treatment and did not appear on the selective plates. To confirm whether the bacteria were inactivated or injured, an enrichment study was done. Neither generic E. coli nor any pathogenic E. coli O157:H7 were detected in the prepared tea in the cup. The hot water temperature was recorded as 82˚C when added in the cup and after 60 seconds the temperature decreased to 78˚ C; further reduced to 73˚C after 3 minutes of holding and at the end of 5 minutes the temperature reached 64˚ C. In addition, the natural microflora was reduced to less than 100 CFU/ml. This finding suggested that addition of hot water (80˚C) in tea leaves resulted in complete elimination of pathogens and thus the present tea making practice could provide safe tea for drinking even though the tea leaves were contaminated. However, for sanitary reasons E. coli should be eliminated from the organic products prior to consumption.

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  • Batch Culture Characterization of Acetogenesis Ruminal Contents: Influence of Acetogen Inocula Concentration and Addition of 2-Bromoethanesulfonic Acid

    Published 10/2014

    Volume 4 Issue 3
    Pp. 177-194

    Keywords: , , , ,

    Abstract:

    nterspecies H2 transfer is a syntrophic interaction between H2-producing and H2-consuming organisms, that plays an important role in regulating ruminal fermentation as well as other ecosystems. Any decrease in hydrogen concentration, due to interspecies hydrogen transfer can influence volatile fatty acid fermentation patterns of many ruminal microorganisms. In the rumen, methanogens consume hydrogen to generate energy and thus serve as a hydrogen sink. However energy is lost due to eructation of methane which can not be used by the ruminant animal.Alternative hydrogen consuming organisms, such as acetogens, could be an attractive alternative hydrogen sink in rumen ecosystems because they generate actetate from hydrogen and carbon dioxide, which can be used by the host animal.However, this would require inhibiting methanogenic activity. Therefore, batch cultures were used to study acetogenesis as a functional alternative to methanogenesis in the rumen in the presence of a methanognesis inhibitor.In batch culture experiments, acetogen strains G1.5a, G2.4a, G3.2a, A10, and 3H were able to reduce H2 concentrations in ruminal contents in the presence of bromoethanesulfonic acid, an inhibitor of methanogenesis.Batch culture studies indicated that acetogens could function as an alternative electron sink to methanogens under some conditions.

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  • The Effect of Phytochemical Tannins-Containing Diet on Rumen Fermentation Characteristics and Microbial Diversity Dynamics in Goats Using 16S rDNA Amplicon Pyrosequencing

    Published 10/2014

    Volume 4 Issue 3
    Pp. 195-211

    Keywords: , , ,

    Abstract:

    Two grazing experiments were performed to 1) investigate the effects of supplementing condensed tanninsontaining pine bark powder on average daily gain, ruminal fermentation, and rumen microbial diversity dynamics (Experiment 1), and 2) to quantify the influence of different sources of extracted tannins supplementations on ruminal fermentation and rumen microbial diversity changes of goats grazing fresh forages (Experiment 2). In experiment 1, 20 Kiko-Boer cross male goats (Capra hircus; initial body weight= 39.7 ± 2.55 kg) were randomly assigned to 2 experimental diets (alfalfa pellet vs. pine bark powder). Alfalfa pellet (no tannin as a control) or pine bark powder (11% condensed tannins) was supplemented at 0.5% body weight for targeted total dry matter intake of 1.2% body weight. The remaining dry matter intake of each diet was obtained from grazing for 55 days. In experiment 2, 12 Kiko-Boer cross goats were used to measure average daily gain, ruminal fermentation, and gut microbial population in the rumen of goats grazing bermudagrass. The animals were randomly assigned to 3 experimental diets: 1) no tannins (control), 2) chestnut extract at 100 g/d, and 3) quebracho tannin extract at 100 g/day. In experiment 1, average daily gain and rumen fermentation status as measure of volatile fatty acids production were similar between diets. Bacterial population in pine bark powder-supplemented group was greater for Bacteroides (20.5 vs. 33.2%) and Firmicutes (67.2 vs. 57.3%) phylum compared with control group, respectively. In experiment 2, average daily gain was greatest (P < 0.05) for chestnut tannins extract (278.6 g/d) than quebracho tannins extract (150 g/d) and the control (42.9 g/d). Goats grazing bermudagrass pasture with chestnut tannins extract had greater (P < 0.05) concentrations of acetate, propionate, butyrate, and total volatile fatty acids compared to those in quebracho tannins extract and control. Bacterial population in chestnut tannins extract-supplemented group was greatest for Bacteroides (51.5, 52.9, and 35.3%) phylum compared with quebracho tannin extract and control group, respectively. Current study shows that tannins from plants can exhibit a positive or negative effect both on rumen fermentation and on rumen microflora, and it is possible that this effect is depending on sources of tannins or tanninontaining diet.

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  • Characterization of the Novel Enterobacter cloacae Strain JD6301 and a Genetically Modified Variant Capable of Producing Extracellular Lipids

    Published 10/2014

    Volume 4 Issue 3
    Pp. 212-223

    Keywords: , , , , , , , , ,

    Abstract:

    This work presents results from the phenotypic and genotypic characterization of a novel Enterobacter cloacae strain (#JD6301) recently isolated from a mixed population of oleaginous microorganisms. Lipid analysis of this strain indicated that JD6301 produces nearly 50% of its cellular weight as lipids. The yield of fatty acid methyl esters for this microorganism was 76 μg/mL. Transmission electron microscopy observations showed inclusion bodies form within this isolate. To improve the recovery of these useful lipids from this microorganism, a random mutagenesis assay was utilized to isolate an alternative form of this bacterium capable of producing extracellular lipids. The extracellular fraction of the mutant strain JD8715 had a total fatty acid methyl esters yield of 86 μg/mL, which was similar to the intracellular yield of JD6301. Furthermore, cell viability and microscopic analysis indicated that the presence of extracellular lipids was not due to cell lysis. Comparative genome analysis of JD8715 against JD6301 revealed 24 single nucleotide polymorphisms, of which 17 resulted in non-synonymous amino acid changes. Seven of these changes occurred in genes related to membrane proteins. The application of oleaginous microorganisms capable of producing extracellular lipids while still retaining cell viability represents a promising approach for providing energy required for iotechnological applications.

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  • Survival of Salmonella enterica and Listeria monocytogenes in manure-based compost mixtures at sublethal temperatures

    Published 10/2014

    Volume 4 Issue 3
    Pp. 224-238

    Keywords: , , , , , , , , ,

    Abstract:

    erobic composting of animal manures has been advocated as an effective management tool to inactivate resident zoonotic pathogens where the time at lethal temperatures is used to determine the effectiveness of the treatment.In the absence of meeting these process conditions, the relative contributions of other physical factors on growth and persistence of zoonotic pathogens is vague and therefore the required storage time necessary for elimination of pathogens cannot be adequately estimated.This study explored the influence of sublethal temperatures, moisture levels, and light exposure on the survival of Salmonella and Listeria monocytogenes in compost mixtures that were prepared with three different sources of manure (dairy cow, swine, and chicken).As ambient temperatures increased from 20°C to 40°C, persistence of both pathogens decreased, which was likely due to the increased competitive activity of the more dominant indigenous microflora. During storage at 30°C, evaporation of water from compost mixtures occurred rapidly.Under those conditions, populations of L. monocytogenes declined in cow compost mixtures throughout a 4-week storage period, whereas Salmonella populations increased.In chicken compost mixtures at 30°C, populations of both pathogens decreased only during the first week of storage, which was likely due to the antimicrobial properties of ammonia initially present in chicken manure.When stored at 20°C, L. monocytogenes populations decreased more rapidly when compost mixtures were exposed to more intense light conditions whereas no discernible differences in Salmonella populations occurred in swine or cow compost mixtures under the different light conditions.These results indicate that developing safety guidelines for times to hold compost mixtures at sublethal temperatures, prior to land application, will be challenging.

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