Catalase and enumeration of stressed Staphylococcus aureus cells.

The effects of catalase on the enumeration of stressed (heated, reduced water activity, or freeze-dried) Staphylococcus aureus cells on several selective media were examined. The addition of catalase greatly increased the enumeration of stressed cells. The beneficial effects of catalase were most pronounced on those media least efficient in enumeration of stressed staphylococci, showing increases in enumeration of up to 1,100-fold. The effects of catalase appear to be due to the reduced ability of stressed cells to repair and form colonies in the absence of an exogenous decomposer of H2O2. Thermally stressed cells were more sensitive to H2O2 than unstressed cells. During recovery, stressed cells overcame the requirement for catalase. These findings implicate H2O2 as a factor in the failure of certain selective media to adequately enumerate stressed cells and demonstrate that the addition of catalase to these media markedly increases their productivity.     

Automation of microbial enumeration: development of a disposable hydrophobic grid-membrane filter unit.

A disposable filter unit containing a hydrophobic grid-membrane filter (HGMF) was developed. The unit is liquid tight to serve as a specimen transport container and, by removal of the funnel extender (175- or 300-ml capacity), the unit becomes less than the height of two stacked petri plates to save space during in situ incubation. The polyethylene mesh which supports the HGMF facilitates rinse removal of any substance(s) that would interfere with microbial growth. The correlations between a pour plate, a conventional square HGMF, and a disposable filter unit on microbial enumeration were examined. Characteristics (e.g., clumping, spreading, etc.) of some microorganisms limit the linear counting range to less than 1,000 CFU per filter.     

Dyes as fungal inhibitors: effect on colony enumeration

The effects of three dyes on the colony enumeration of nine fungal strains (including members of the Deuteromycetes and Zygomycetes) in pure and mixed cultures were investigated. Using malt extract agar as basal and control medium, the following dyes and concentrations were assayed: auramine (25 ppm), gentian violet (5 ppm) and malachite green (1 ppm). The chemicals commonly used in commercial media dichloran (2 ppm) and rose bengal (50 ppm) were included in the study as reference mould-spreading inhibitors. Higher counts were usually obtained in the media containing dichloran, rose bengal or auramine, including the control medium in the absence of chemical when the mixed-conidium inocula did not include a spreading mould. Nevertheless in most cases no significant differences were observed between them. Malachite green (1 ppm) performed mainly as a strong inhibitor of spreading moulds, only allowing adequate colony development and recoveries of both Fusarium and Aspergillus strains tested.     

The effect of viewing eccentricity on enumeration

Visual acuity and contrast sensitivity progressively diminish with increasing viewing eccentricity. Here we evaluated how visual enumeration is affected by visual eccentricity, and whether subitizing capacity, the accurate enumeration of a small number (～3) of items, decreases with more eccentric viewing. Participants enumerated gratings whose (1) stimulus size was constant across eccentricity, and (2) whose stimulus size scaled by a cortical magnification factor across eccentricity. While we found that enumeration accuracy and precision decreased with increasing eccentricity, cortical magnification scaling of size neutralized the deleterious effects of increasing eccentricity. We found that size scaling did not affect subitizing capacities, which were nearly constant across all eccentricities. We also found that size scaling modulated the variation coefficients, a normalized metric of enumeration precision, defined as the standard deviation divided by the mean response. Our results show that the inaccuracy and imprecision associated with increasing viewing eccentricity is due to limitations in spatial resolution. Moreover, our results also support the notion that the precise number system is restricted to small numerosities (represented by the subitizing limit), while the approximate number system extends across both small and large numerosities (indexed by variation coefficients) at large eccentricities.     

Automated statistical analysis of microbial enumeration by dilution series

Equations are formulated for the standard error and confidence interval for the MPN estimate of microbial density from a general dilution series. A statistical test of homogeneity is presented. This tests whether a handling error in the dilution series may have occurred which would invalidate the density estimate. The analysis may be automated using a Basic computer program which contains a fast algorithm for the solution of the general MPN equation. This allows the calculation of the MPN, standard error, 95% confidence interval and test statistic for any dilution series, with any degree of replication at each dilution level, with variable sample volumes at each dilution level, with variable dilution ratio between levels, and with any number of levels.     

Indirect conductimetry: a novel approach to the conductimetric enumeration of microbial populations

A method is described for the indirect conductimetric assessment of microbial populations by the absorption of metabolic CO₂ in an alkaline absorbent solution whose conductance is monitored. The method allows microbial growth in un-modified conventional culture media to be monitored conductimetrically.     

Automation of microbial enumeration: development of a disposable hydrophobic grid-membrane filter unit

A disposable filter unit containing a hydrophobic grid-membrane filter (HGMF) was developed. The unit is liquid tight to serve as a specimen transport container and, by removal of the funnel extender (175- or 300-ml capacity), the unit becomes less than the height of two stacked petri plates to save space during in situ incubation. The polyethylene mesh which supports the HGMF facilitates rinse removal of any substance(s) that would interfere with microbial growth. The correlations between a pour plate, a conventional square HGMF, and a disposable filter unit on microbial enumeration were examined. Characteristics (e.g., clumping, spreading, etc.) of some microorganisms limit the linear counting range to less than 1,000 CFU per filter.     

Catalase protects cardiomyocytes via its inhibition of nitric oxide synthesis.

Nitric oxide (NO) has been reported to play an important role as an effector molecule in cytokine signal transduction in cardiomyocytes. A treatment of neonatal rat ventricular cardiomyocytes with interleukin-1 beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) induces apoptosis via an NO-dependent pathway. However, cardiomyocytes were more resistant to NO-dependent cell death in the presence of catalase, while producing inducible nitric oxide synthase. This paper reports that catalase stimulates the NF-kappaB-binding affinity. However, the NO synthase activity is abolished by the addition of catalase, suggesting that H(2)O(2) is involved in NO synthesis in a posttranslation state. The catalase-induced inhibition of NO was partially but significantly reversed by H(4)B, an important cofactor of NO synthesis. Treatment of myocytes with IL-1beta, TNF-alpha, and IFN-gamma induced a significant increase in the formation of peroxynitrite, and a pretreatment with catalase was found to quench the production of peroxynitrite. This paper shows that the catalase activity was significantly down-regulated by H(4)B in a concentration-dependent manner. The treatment of H(4)B induced reactive oxygen species (ROS) release in cardiac cell system. These results suggest that catalase interferes with NO and peroxynitrite production as well as with the related apoptosis of cardiomyocytes. This study also shows that the catalase-induced inhibition of NO release may be reversed by H(4)B by the release of ROS.     

Use of a microbial fuel cell for the rapid enumeration of bacteria

Summary The detection of bacteria using a thionine mediated microbial fuel cell was examined. On addition of bacteria to the anode compartment of a fuel cell, a rapid increase in the current output was observed. Both the total change in the steady state current (mA) and the initial rate of change of current were proportional to the numbers of bacteria added. Regression analysis of plots of log₁₀ mA against log₁₀ bacteria ml^-1 (final concentration) upon the addition of E. coli K12, Lactococcus lactis, coliform sp. A1, Micrococcus sp. M3 but not Pseudomonas sp. P5 gave reasonable correlation coefficients. Determination of the rates of respiration and thionine reduction by E. coli indicated that the transfer of metabolic electrons from the bacteria to the mediator was reasonably efficient (approx. 50%). These results are discussed with respect to the potential application of this technique for the rapid estimation of the bacterial contamination of foods.     

The microbial degradation of azimsulfuron and its effect on the soil bacterial community

AIMS: Azimsulfuron is a recently introduced sulfonylurea herbicide useful in controlling weeds in paddy fields. To date very little information is available on the biodegradation of this pesticide and on its effect on the soil microbial community. The aim of this work was to study its biodegradation both in slurry soil microcosms and in batch tests with mixed and pure cultures. METHODS AND RESULTS: Azimsulfuron was applied to forest bulk soil in order to study its effect on the structure of the bacterial soil community, as detectable by denaturant gradient gel electrophoresis (DGGE) analyses. Biodegradation and abiotic processes were investigated by HPLC analyses. In addition, a microbial consortium was selected, that was able to use azimsulfuron as the sole energy and carbon source. One of the metabolites produced by the consortium was isolated and identified through LC-MS analyses. Cultivable bacteria of the consortium were isolated and identified by 16S rDNA sequencing (1400 bp). CONCLUSIONS: Azimsulfuron treatment seems to have the ability to cause changes in the bacterial community structure that are detectable by DGGE analyses. It is easily biodegraded both in microcosms and in batch tests, with the formation of an intermediate that was identified as 2-methyl-4-(2-methyl-2H-tetrazol-5-yl)-2H-pyrazole-3-sulfonamide. SIGNIFICANCE AND IMPACT OF THE STUDY: The study increases the knowledge on the biodegradation of azimsulfuron and its effects on the soil microbiota.     

Catalase encapsulated in mesoporous silica and its performance

Catalase was confined in a nanospace of about 7 nm in diameter in mesoporous silica (FSM; folded-sheet mesoporous material), forming a catalase-FSM conjugate. That the enzyme was encapsulated in the pores of mesoporous materials was proven by the direct visualization technique. The catalase-FSM showed not only an activity similar to that of the native catalase in the decomposition of H₂O₂ but also much higher stability: specifically, the catalase immobilized in FSM still retained its original activity after being applied 50 times to the decomposition, whereas the native lost its activity after 20 times recycling. Furthermore, the catalase-FSM showed catalase activity even in an organic media in which the native catalase had almost no catalytic activity.     

Catalase activity in human erythrocytes: effect of phenoxyherbicides and their metabolites

The effects of exposure to different concentrations of phenoxyherbicides and their metabolites were studied in human erythrocytes, with particular attention to catalase (CAT-EC. 1.11.1. 6- hydrogen peroxide: hydrogen peroxide oxidoreductase). 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,4-dimethylphenol (2, 4-DMP) and 2,4-dichlorophenoxyacetic acid (2,4-D) did not affect CAT activity, but 2,4-dichlorophenol (2,4-DCP) and 2,4,5-trichlorophenol (2,4,5-TCP) decrease its activity, the latter being the more inhibitory.     

A defined substrate technology for the enumeration of microbial indicators of environmental pollution

The examination of water and other environmental sources for microbial pollution is a major public health undertaking. Currently, there are two accepted methods in use: the multiple-tube fermentation (MTF) and the membrane filtration (MF) tests. Both methods are designed to enumerate the secondary indicator group, total coliforms. Both tests suffer several inherent limitations, including a time delay of three to seven days to obtain a definitive result, the subjective nature of the test interpretation, and the inability to provide directly useful public health information. A defined substrate technology, originally used to enumerate specific bacterial species from mixtures in clinical urine specimens, was applied to water testing; the technology was constituted to enumerate simultaneously both total coliforms and the primary indicator bacterium E. coli. Examination of environmental isolates of these two classes of target microbes showed sensitivity equal to available methods, with potentially greater specificity. It was not subject to inhibition by bacteria other than the targets, grew injured coliforms, did not require confirmatory tests, and the maximum time to a positive was 24 hours. The defined substrate technology provides both regulatory and directly useful public health information.     

The cumulative effect of gamma irradiation on the microbial soil population and its activity

The counts ofAzotobacter, N-fixing clostridia, aerobic cellulose decomposing bacteria, spore formers and actinomycetes were not affected by examined irradiation doses. There were, however, indications of a disturbance in the balance between organisms as evidenced by the rapid increase of actinomycetes and sporeformers during incubation. The effects of various irradiation doses on organic matter decomposition, N-fixing capacity and nitrification power were negligible.     

Catalase in skeletal muscle fibers.

Catalase has been localized immunocytochemically with anti-bovine catalase in long thin filament structures in aerobic type I fibers in the skeletal muscles of normal and genetically dystrophic hamsters. The filaments range in length from 1 to 60 micron, are orientated regularly along the long axis of the fibers, and also seem to surround and project from muscle nuclei. The enzyme thus appears to be more prominent in the sarcoplasmic reticulum than in peroxisomes, and in this situation is suitably placed for destroying toxic hydrogen peroxide which may be continously generated in aerobic fibers.     

内源微生物驱油及其对油藏微生物活动的影响

【目的】新疆油田六中区为典型水驱普通稠油油藏,水驱效果较差,油藏具有丰富的内源微生物,本研究通过分析内源微生物驱油对油藏微生物活动的影响,确定内源微生物驱油技术在该类油藏的应用潜力。【方法】采用高通量测序及分析化学技术,系统研究实施内源微生物驱油技术后油藏细菌群落结构组成、细菌总数和功能菌群的浓度以及采出液的流体性质,总结内源微生物驱油对油藏微生物活动的影响。【结果】现场试验注入激活剂和空气后,内源微生物被显著激活,细菌群落结构发生明显变化,细菌总数及功能菌群浓度普遍提高了2–3个数量级;各种内源微生物代谢活动显著增强,与地层流体相互作用后,原油明显被乳化,最终石油采收率提高5.2%。【结论】对于内源微生物较为丰富的水驱普通稠油油藏,内源微生物驱油技术对油藏微生物活动的影响显著,具有显著的技术优势和较大的应用潜力,微生物群落结构、功能菌群浓度及其相关代谢产物可以作为评价内源微生物驱油现场激活效果的重要指标,为其他内源微生物驱油现场试验提供技术参考。     

Influence of 3-chloropropane-1,2-diol on microbial lipid composition and its effect on the activity of some antibacterial agents.

The organisms E. coli, S. aureus, K. aerogenes, Pr. vulgaris and S. abortusovis were inhibited by 3-chloropropane-1,2-diol at high concentrations (ca 10,000 mug/ml) and Ps. aeruginosa was unaffected. The phospholipid and lipoamino acid composition of E. coli, S. aureus and S. cerevisiae was altered by growth in the presence of 3-chloropropane-1,2-diol. The effect of growth under these conditions on the sensitivity of the bacteria to various antibacterial agents was determined and appears to depend on the hydrophobicity of the drug molecule. Cell division of E. coli and S. aureus was impaired by growth in the presence of 3-chloropropane-1,2-diol leading to filamentous forms. The change in phospholipid composition of both Gram-positive and Gram-negative organisms may influence cell division and antibiotic sensitivity.     

Starch hydrolysis and its effect on product yield and microbial contamination in yeast ethanol fermentation

The influence of temperature and incubation time on starch gelatinization in wheat, rye and corn grain were studied. Rye starch was the most susceptlble to enzyme hydrolysls. Heat treatment of ground grain during starch gelatinlzation significantly reduced microblal contamination. In the batch fermentation of wheat, a high sugar utillization ranged from 92 to 94%. The highest alcohol yield was 65% from rye starch. The results obtained show that the high pressure cooking used for mash preparation can be replaced successfully by low temperature treatment.The authors are with the Institute of Food Technology of Plant Origin, The University of Agriculture, 60-624 Poznan, ul. Wojska Polskiego 31, Poland.