scholarly journals Molecular Methods for Assessement the Bacterial Communities from Different Type of Soils in Romania

2011 ◽  
Vol 39 (1) ◽  
pp. 64 ◽  
Author(s):  
Călina Petruţa CORNEA ◽  
Cătălina VOAIDEŞ ◽  
Matilda CIUCA ◽  
Vasilica STAN ◽  
Eugenia GAMENT ◽  
...  
Keyword(s):  
Plant Species ◽  
Host Plants ◽  
Root Nodules ◽  
Indigenous Populations ◽  
Most Probable Number ◽  
Organic Carbon Content ◽  
Bacterial Strains ◽  
Probable Number ◽  
Plate Counts ◽  
Fertilization Level

Rhizobia are soil bacteria that are capable to form nitrogen-fixing symbiosis with leguminous plants. This ability, as well as the diversity of microbial populations in the soil, and in the rhizosphere of host plants and non-host plants is influenced by several factors, including crop management. The aim of this work was the examination of the influence of some factors on indigenous populations of rhizobia in soils under different crop managements. The genetic diversity of rhizobial strains isolated directly from soil (free-living state) or from root nodules of three herbaceous perennial legumes was examined. The study was conducted in the experimental fields located in Moara Domnească area (South of Romania) and in the Brașov County. The characteristics of brown reddish soil were determined (nitrogen content, organic carbon content and pH). Counting of the rhizobia populations was done by most probable number estimation and by viable plate counts. Bacterial strains were isolated directly from soil samples or from root nodules of different plant species (Trifolium repens, T. pratense and Lotus corniculatus). The characterization of rhizobia was performed by DNA fingerprinting (ERIC PCR and BOX PCR) and the bacterial diversity of soils was examined by DGGE technique. The results revealed that the rhizobial diversity was significantly lower in soils under increased fertilization with N. A reduced intraspecific polymorphism was observed in the strains recovered from the same plant species (Trifolium spp.), whatever the origin of the plant (Moara Domnească or Brașov) but clear differences appeared to be related to the origin of nodules (red or white clover) as revealed by DNA fingerprints. However, various amplicon profiles were observed by DGGE when total DNA isolated from soils was examined, the differences being associated with the fertilization level.

The Occurrence of Legionella Bacteria in Cooling Towers in South Africa

1991 ◽  
Vol 24 (2) ◽  
pp. 149-152 ◽  
Author(s):  
N. A. Grabow ◽  
E. J. Pienaar ◽  
R. Kfir
Keyword(s):  
South Africa ◽  
Most Probable Number ◽  
Cooling Towers ◽  
Probable Number ◽  
Service Water ◽  
Standard Plate ◽  
Viable Bacteria ◽  
Plate Counts ◽  
High Level ◽  
Biocide Treatment

A total of 510 service water samples from cooling towers throughout South Africa were analysed for the presence of Legionella bacteria. Legionella was detected using an immuno-labelling technique based on the most probable number principle. Only cultural (viable) bacteria were counted. Legionellae were found in most of the samples tested. However, in only 4% of the samples a high level of legionellae was recorded. No correlation was found between the numbers of legionellae and those of standard plate counts. Biocide treatment was shown to be effective in the removal of the bacteria from cooling towers after a 3-month treatment period.

scholarly journals Fabrication and Characterization of Antimicrobial Magnetron Cosputtered TiO2/Ag/Cu Composite Coatings

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 473
Author(s):  
Dilyana Gospodonova ◽  
Iliana Ivanova ◽  
Todorka Vladkova
Keyword(s):  
Antimicrobial Activity ◽  
Composite Coatings ◽  
Surface Characteristics ◽  
Standard Test ◽  
Most Probable Number ◽  
Bacterial Strains ◽  
Probable Number ◽  
Fabrication And Characterization

The aim of this study was to prepare TiO2/Ag/Cu magnetron co-sputtered coatings with controlled characteristics and to correlate them with the antimicrobial activity of the coated glass samples. The elemental composition and distribution, surface morphology, wettability, surface energy and its component were estimated as the surface characteristics influencing the bioadhesion. Well expressed, specific, Ag/Cu concentration-dependent antimicrobial activity in vitro was demonstrated toward Gram-negative and Gram-positive standard test bacterial strains both by diffusion 21 assay and by Most Probable Number of surviving cells. Direct contact and eluted silver/coper nanoparticles killing were experimentally demonstrated as a mode of the antimicrobial action of the studied TiO2/Ag/Cu thin composite coatings. It is expected that they would ensure a broad spectrum bactericidal activity during the indwelling of the coated medical devices and for at least 12 h after that, with the supposition that the benefits will be over a longer time.

Reduction of Microorganisms on Citrus Fruit Surfaces during Packinghouse Processing

1998 ◽  
Vol 61 (7) ◽  
pp. 903-906 ◽  
Author(s):  
STEVEN PAO ◽  
G. ELDON BROWN
Keyword(s):  
Test Organism ◽  
Citrus Fruit ◽  
Microbial Populations ◽  
Most Probable Number ◽  
Probable Number ◽  
E Coli ◽  
Plate Counts ◽  
High Level ◽  
Inoculation Study ◽  
Fruit Surface

Citrus fruit surface microbial populations were evaluated following various packingline processes of seven Florida commercial packinghouses. At each packinghouse, six fruits (oranges or tangerines) were collected at each of four sampling points. The sampling was conducted in duplicate; thus, 336 fruit were evaluated during this survey. Average aerobic plate counts and yeast and mold counts on fruit surfaces before washing were about 4.0 log CFU/cm2 and 3.3 log CFU/cm2, respectively, and were reduced to 2.1 log CFU/cm2 and 1.3 log CFU/cm2, respectively, by packinghouse processing. Waxing alone reduced the average fruit surface aerobic plate counts and coliform counts from 3.7 log CFU/cm2 and 35.2 most probable number (MPN)/cm2, respectively, to 2.6 log CFU/cm2 and 1.4 MPN/cm2. No Escherichia coli was recovered from fruit at the end of packinghouse processing, and no salmonellae were found on fruit during the entire processing. In an inoculation study to test the effect of packinghouse processes, test organism E. coli was applied to fruit to achieve a high level (4.8 log CFU/cm2) of contamination. The average E. coli count was reduced about 2.4 log cycles by washing and rinsing with potable water (40 psi, 25 °C) for about 30 s. The combination of washing and waxing significantly reduced the inoculated level of E. coli from 4.8 to 1.4 log CFU/cm2.

A Bacteriological Survey of Raw Ground Beef1

1977 ◽  
Vol 40 (11) ◽  
pp. 790-794 ◽  
Author(s):  
JAMES F. FOSTER ◽  
JAMES L. FOWLER ◽  
WARREN C. LADIGES
Keyword(s):  
Escherichia Coli ◽  
Microbiological Quality ◽  
Retail Store ◽  
Most Probable Number ◽  
Probable Number ◽  
E Coli ◽  
Fecal Streptococci ◽  
Plate Counts ◽  
Aerobic And Anaerobic

The microbiological quality of 150 units of raw ground beef obtained from a local retail store was determined. The range of aerobic plate counts was from 6.9 × 104 to 8.3 × 107/g. By using the most probable number method 96.7% of the 150 units were positive for coliforms, 94.7% for Escherichia coli and 61.3% for Staphylococcus aureus. By the plate methods, 99.3% of the units were positive for fecal streptococci and 56% were positive for Clostridium perfringens. No salmonellae were isolated. Aerobic and anaerobic organisms were isolated and identified. E. coli was the most frequently isolated aerobe followed by organisms in the Klebsiella-Enterobacter group. Among the anaerobic isolates, C. perfringens was the organism most frequently encountered.

Selective enumeration of aromatic and aliphatic hydrocarbon degrading bacteria by a most-probable-number procedure

1996 ◽  
Vol 42 (3) ◽  
pp. 252-258 ◽  
Author(s):  
Brian A. Wrenn ◽  
Albert D. Venosa
Keyword(s):  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Oxidation Products ◽  
Most Probable Number ◽  
Probable Number ◽  
Microtiter Plates ◽  
Degrading Bacteria ◽  
Polycyclic Aromatic ◽  
Pure Cultures ◽  
Plate Counts

A most-probable-number (MPN) procedure was developed to separately enumerate aliphatic and aromatic hydrocarbon degrading bacteria, because most of the currently available methods are unable to distinguish between these two groups. Separate 96-well microtiter plates are used to estimate the sizes of these two populations. The alkane-degrader MPN method uses hexadecane as the selective growth substrate and positive wells are detected by reduction of iodonitrotetrazolium violet, which is added after incubation for 2 weeks at 20 °C. Polycyclic aromatic hydrocarbon degraders are grown on a mixture of phenanthrene, anthracene, fluorene, and dibenzothiophene in a second plate. Positive wells turn yellow to greenish-brown from accumulation of the partial oxidation products of the aromatic substrates and they can be scored after a 3-week incubation period. These MPN procedures are accurate and selective. For pure cultures, heterotrophic plate counts on a nonselective medium and the appropriate MPN procedure provide similar estimates of the population density. Bacteria that cannot grow on the selective substrates do not produce false positive responses even when the inoculum density is very high. Thus, this method, which is simple enough for use in the field, provides reliable estimates for the density and composition of hydrocarbon-degrading microbial populations.Key words: most probable number, polycyclic aromatic hydrocarbon, alkane, hydrocarbon, bacteria.

Levels and Enterotoxigenicity of Clostridium perfringens in Pozole, Tamales, and Birria

2005 ◽  
Vol 68 (2) ◽  
pp. 331-335 ◽  
Author(s):  
V. NAVARRO-HIDALGO ◽  
E. CABRERA-DÍAZ ◽  
H. ZEPEDA ◽  
L. MOTA DE LA GARZA ◽  
A. CASTILLO ◽  
...  
Keyword(s):  
Clostridium Perfringens ◽  
Cell Elongation ◽  
Cytotoxic Effect ◽  
Cell Lysis ◽  
Vero Cells ◽  
Plate Count ◽  
Most Probable Number ◽  
Probable Number ◽  
Quantitative Survey ◽  
Plate Counts

A quantitative survey of Clostridium perfringens in typical foods served at local restaurants was conducted for 18 months in Guadalajara, Mexico. A total of 151 samples, including goat's birria (50), pozole (50), and beef tamales (51), were collected from small restaurants in Guadalajara. Samples were tested for C. perfringens by the most probable number (MPN) method and for mesophilic aerobic plate counts (MAPCs) and coliform, yeast, and mold counts by plate count methods. Isolates confirmed as C. perfringens were further sporulated and tested for cytotoxic or cytotonic effect against Vero cells as an indication of enterotoxin production. C. perfringens was detected in 78 (52%) of all samples at concentrations that ranged from 2.3 to 5.4 log MPN/g. Average MAPCs were 1.3 to 2.7 log CFU/g, depending on the type of dish. Coliform counts ranged from less than 1.0 to 1.5 CFU/g, and yeast and mold counts were less than 1.0 log CFU/g in all cases. A total of 118 isolates of C. perfringens were tested for enterotoxic effect on Vero cells; 82 (70%) showed activity against Vero cells. Of them, 31 isolates induced cell lysis, indicating cytotoxic effect; 41 induced cell elongation, indicating cytotonic effect; and 10 produced both cytotoxic and cytotonic effect. Dilution of the bacterial filtrates that were still producing an effect on Vero cells ranged from 1:80 to 1:5,120. These results underscore the importance of determining enterotoxigenicity when testing for C. perfringens in foods.

scholarly journals Enhanced Mineralization of [U-14C]2,4-Dichlorophenoxyacetic Acid in Soil from the Rhizosphere of Trifolium pratense

2004 ◽  
Vol 70 (8) ◽  
pp. 4766-4774 ◽  
Author(s):  
Liz J. Shaw ◽  
Richard G. Burns
Keyword(s):  
Plant Species ◽  
Trifolium Pratense ◽  
Rhizosphere Soil ◽  
Most Probable Number ◽  
Dichlorophenoxyacetic Acid ◽  
Polymorphism Analysis ◽  
Alternative Mechanism ◽  
Probable Number ◽  
Enhanced Biodegradation ◽  
2,4 Dichlorophenoxyacetic Acid

ABSTRACT Enhanced biodegradation in the rhizosphere has been reported for many organic xenobiotic compounds, although the mechanisms are not fully understood. The purpose of this study was to discover whether rhizosphere-enhanced biodegradation is due to selective enrichment of degraders through growth on compounds produced by rhizodeposition. We monitored the mineralization of [U-14C]2,4-dichlorophenoxyacetic acid (2,4-D) in rhizosphere soil with no history of herbicide application collected over a period of 0 to 116 days after sowing of Lolium perenne and Trifolium pratense. The relationships between the mineralization kinetics, the number of 2,4-D degraders, and the diversity of genes encoding 2,4-D/α-ketoglutarate dioxygenase (tfdA) were investigated. The rhizosphere effect on [14C]2,4-D mineralization (50 μg g−1) was shown to be plant species and plant age specific. In comparison with nonplanted soil, there were significant (P < 0.05) reductions in the lag phase and enhancements of the maximum mineralization rate for 25- and 60-day T. pratense soil but not for 116-day T. pratense rhizosphere soil or for L. perenne rhizosphere soil of any age. Numbers of 2,4-D degraders in planted and nonplanted soil were low (most probable number, <100 g−1) and were not related to plant species or age. Single-strand conformational polymorphism analysis showed that plant species had no impact on the diversity of α-Proteobacteria tfdA-like genes, although an impact of 2,4-D application was recorded. Our results indicate that enhanced mineralization in T. pratense rhizosphere soil is not due to enrichment of 2,4-D-degrading microorganisms by rhizodeposits. We suggest an alternative mechanism in which one or more components of the rhizodeposits induce the 2,4-D pathway.

Microbiological Quality of Powdered Infant Formula in Latin America

2020 ◽  
Vol 83 (3) ◽  
pp. 534-541 ◽  
Author(s):  
JULIO PARRA-FLORES ◽  
EDUARD MAURY-SINTJAGO ◽  
ALEJANDRA RODRIGUEZ-FERNÁNDEZ ◽  
SERGIO ACUÑA ◽  
FABIOLA CERDA ◽  
...  
Keyword(s):  
Infant Formula ◽  
Protein A ◽  
Microbiological Quality ◽  
Most Probable Number ◽  
Powdered Infant Formula ◽  
Probable Number ◽  
Antibiotic Resistance Profile ◽  
Plate Counts

ABSTRACT Cronobacter is a bacterial genus that includes seven species, and the species Cronobacter sakazakii is most related to meningitis and septicemia in infants associated with powdered infant formula (PIF). The objectives of this study were to evaluate the presence of C. sakazakii and to determine the microbiological quality of PIF for infant consumption. To do this, a total of 128 PIF samples were analyzed in four brands and countries (Chile, Mexico, Holland, and Brazil), considering three types of PIF: premature (PIF1), infant (PIF2), and follow-up (PIF3). Aerobic plate counts (APC) and Enterobacteriaceae (ENT) were assessed in accordance with Chilean official standards. The outer membrane protein A (ompA) gene was amplified to detect Cronobacter spp. and the fusA gene was amplified to identify C. sakazakii by using the PubMLST Web site and BLAST (NCBI). The antibiotic resistance profile was performed according to the Clinical and Laboratory Standards Institute standards. The pathogen was quantified by the most probable number (MPN). The results showed that APC median values for PIF1, PIF2, and PIF3 were 3.2, 4.9, and 4.8 log CFU g−1, respectively. The APC were higher in PIF2 (P &lt; 0.01) from Holland (P &lt; 0.01) in the commercial brand 4 (P &lt; 0.01). The ENT median values in PIF1, PIF2, and PIF3 were 1.8, 1.5, and 1.7 log CFU g−1, respectively. Five strains of C. sakazakii and one strain of Cronobacter malonaticus were identified as having values between 0.023 and 2.3 MPN/g. All strains (100%) harbored the ompA, plasminogen activator (cpa), and hemolysin (hly) virulence genes. To conclude, C. sakazakii was found in four PIF samples from four Chilean products and one from Mexico, which is distributed throughout America. C. sakazakii strains exhibit virulence factors and resistance to ampicillin, thus posing a risk when PIFs are consumed by infants. HIGHLIGHTS

Studies on mycorrhizal associations in Harvard Forest, Massachusetts

1989 ◽  
Vol 67 (8) ◽  
pp. 2245-2251 ◽  
Author(s):  
Ruhama Berliner ◽  
John G. Torrey
Keyword(s):  
Plant Species ◽  
Most Probable Number ◽  
Probable Number ◽  
Harvard Forest ◽  
Mycorrhizal Associations ◽  
Monotropoid Mycorrhiza ◽  
Vesicular Arbuscular ◽  
Low Diversity ◽  
Different Types ◽  
Good Proportion

An estimate was made of the abundance of different types of mycorrhizal associations in two plant communities of conifers and hardwoods in the Harvard Forest. Lists of plant species, the coverage of their foliage in the canopy and understorey layers, and the types of mycorrhizal associations for 45 species common in these communities are presented. Of the species examined, 91 % were mycorrhizal, representing most of the known major types, viz. ectomycorrhiza, vesicular–arbuscular mycorrhiza (VAM), ericoid, and monotropoid mycorrhiza. Of the 45 species studied, 22% of the species showed ectomycorrhizal, and 71 % VAM associations. A direct spore count was a more reliable method than the most probable number method for determining VAM occurrence in the soil. Spore numbers ranged from 4.4 to 11.8 spores/g oven-dried soil. In conifer stands, ectomycorrhizae were most common, although VAM were also observed in the conifer species. In hardwood stands, VAM were more frequent than in conifer stands, but mycorrhizae were heterogeneous and included a good proportion of the ericoid type. Ectomycorrhizae were more common in communities of low diversity; VAM occurred more frequently in communities of high plant species diversity.

Assessment of Microbiological and Chemical Quality of Bubble Tea Beverages Vended in Taiwan

2019 ◽  
Vol 82 (8) ◽  
pp. 1384-1389 ◽  
Author(s):  
CHUNG-SAINT LIN ◽  
CHIA-JU YANG ◽  
PEI-JU CHEN ◽  
KANG-WEI LIU ◽  
HSI-PIN LIN ◽  
...  
Keyword(s):  
Food Labeling ◽  
Most Probable Number ◽  
Chemical Quality ◽  
Tea Leaves ◽  
Probable Number ◽  
Labeling Regulations ◽  
Plate Counts ◽  
Southern Taiwan ◽  
Central Taiwan

ABSTRACT Bubble tea beverages (n = 105) purchased from vendors in Taiwan were tested to determine their microbiological and chemical quality. Nearly half of the tested samples (48.6%, 51 of 105) had aerobic plate counts (APCs) higher than the Taiwan Food and Drug Administration guideline of 4.0 log CFU/mL, and 55 (52.4%) had coliform counts (most probable number [MPN]) higher than the 10 MPN/mL guideline. Escherichia coli, Salmonella, Staphylococcus aureus, sweeteners, preservatives, maleic acid, and coumarin were not detected in any sample. However, catechins were not detected to 188 mg/mL, and caffeine was 10.1 to 457.6 mg/mL. Bubble tea samples obtained from vendors in southern Taiwan had a mean APC of 2.6 log CFU/mL and a mean coliform count of 61.7 MPN/mL; these values were significantly lower (P &lt; 0.05) than those from samples collected from vendors in northern, eastern, or central Taiwan. Samples obtained from southern Taiwan had the highest mean catechin concentrations of 21.3 mg/mL (P &lt; 0.05). About 60% (63 of 105) of the bubble tea samples were not labeled with the origin of the tea leaves, which is in violation of Taiwanese food labeling regulations. In general, the bubble tea beverages tested had satisfactory microbial and chemical qualities.

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