Persistence of vegetative and sporulated forms of Clostridium perfringens exposed to air at different relative humidities.

Summary In this study the hypothesis that a variation in air humidity will reduce the negative effect of continuous lighting on keeping quality of cut roses without enhancing the development of powdery mildew, was evaluated. Vase life and water loss from detached leaves were studied in two cut rose cultivars grown at daily periods of 0, 6, 12 and 24 h at 62% combined with 82% relative air humidity (RH) under continuous lighting. In addition, the effect of constant low (62% RH) and constant high (82% RH) was studied at 18 h day -1 lighting period. In continuous light, six hours with low RH considerably increased the vase life as compared with constant high RH in both cultivars. Extending the period with low RH from 12 to 24 h decreased the vase life particularly in cv. 'Orange Unique'. Reducing the lighting period from 24 to 18 h day -1 significantly increased the vase life both at low and high RH. A close relationship was found between the vase life and control of leaf water loss from detached leaves in the different treatments. Reducing the lighting period increased the vase life and decreased the water loss from the leaves both at constant low and constant high air humidity. The development of powdery mildew was significantly reduced when the lighting period was increased from 18 to 24 h day -1 . The results are discussed in relation to produce cut roses with long vase life at a greenhouse climate that causes a minimum of powdery mildew development.

Fusobacteria have been suspected to be pathobionts of colon cancer and inflammatory bowel disease. However, the immunomodulatory properties that affect these inflammatory reactions in dendritic cells (DCs) under anaerobic and aerobic conditions have not yet been characterized. We directly assessed the stimulatory effects of anaerobic commensal bacteria, including fusobacteria, on a human DC line through coculture under aerobic or anaerobic conditions. Under aerobic or anaerobic conditions, stimulation of the DC line with all live commensal bacteria examined, except the probiotic Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus), significantly increased the geometric mean fluorescent intensity (MFI) of marker proteins (HLA-ABC, HLA-DR, CD80, CD86, CD83, or CCR7) on the DC surface. In particular, both Fusobacterium nucleatum (F. nucleatum) and Escherichia coli (E. coli) significantly increased the expression of DC-associated molecules, except for CD83 under both aerobic and anaerobic conditions. The DC line stimulated with Fusobacterium varium (F. varium) significantly increased only CD80, HLA-ABC, and HLA-DR expression under anaerobic conditions. Moreover, differences in the levels of proinflammatory cytokines, such as IL-6, IL-8, and TNF-α, were detected in the DC line stimulated by all live commensal bacteria under either aerobic or anaerobic conditions. Under aerobic conditions, the DC line stimulated with E. coli produced significantly more IL-6, IL-8, and TNF-α than did the cells stimulated with any of the bacteria examined. When E. coli were used to stimulate the DC line under anaerobic conditions, TNF-α was predominantly produced compared to stimulation with any other bacteria. Compared to the DC line stimulated with any other bacteria, the cells stimulated with F. nucleatum showed significantly increased production of IL-6, IL-8 and TNF-α only under anaerobic conditions. In particular, E. coli, F. nucleatum, and F. varium strongly stimulated the DC line, resulting in significantly increased expression of surface molecules associated with DCs and production of inflammatory cytokines.

Summary This paper examines whether retention of partially hydrolyzed polyacrylamide (HPAM) is different under anaerobic vs. aerobic conditions. Both static (mixing with loose sand) and dynamic methods (corefloods) were used to determine HPAM retention. There are both advantages and disadvantages associated with determining polymer retention with static tests vs. dynamic tests and with aerobic vs. anaerobic conditions. From static-retention measurements, polymer-adsorption values on pure silica sand or Berea sandstone were small, and they showed little difference between experiments conducted aerobically or anaerobically. For both aerobic and anaerobic conditions, HPAM retention increased significantly with increased pyrite or siderite content. Static retention under anaerobic conditions ranged from 45 to 75 µg/g with 1% of either pyrite or siderite to 137–174 µg/g for 10% pyrite or siderite to 1161–1249 µg/g for 100% pyrite or siderite. If iron minerals are present, the most representative polymer-retention results are obtained (for both static and dynamic tests) if conditions are anaerobic. Retention values (from static measurements) under aerobic conditions were commonly twice those determined under anaerobic conditions. If iron minerals are present and retention tests are performed under aerobic conditions, total organic carbon (TOC) or some similar method should be used for polymer detection. Viscosity detection of polymer may provide retention values that are too high (because oxidative degradation can be misinterpreted as polymer retention). For a broad range of siderite content, retention from static tests did not depend on whether dissolved oxygen was present. However, for a broad range of pyrite content, HPAM retention was significantly lower in the absence of dissolved oxygen than under aerobic conditions. These results may be tied to iron solubility. When polymer solutions were mixed with 100% pyrite over the course of 12 hours, 360–480 ppm of iron dissolved into polymer solutions under both aerobic and anaerobic conditions, whereas with 100% siderite, only 0.0–0.6 ppm of iron dissolved. If dynamic methods (i.e., corefloods) are used to determine polymer retention under aerobic conditions, flow rates should be representative of the field application. Rates that are too high lead to underestimation of polymer retention. With 10% pyrite, dynamic retention was 211 µg/g at 6 ft/D vs. 43.2 µg/g at 30 ft/D. In contrast, retention values were fairly consistent (40.6–47.8 µg/g) between 6 and 33 ft/D under anaerobic conditions.

An anaerobic rhizobacterium primes rice immunity.

This paper examines whether retention of partially hydrolyzed polyacrylamide (HPAM) is different under anaerobic versus aerobic conditions. Both static (mixing with loose sand) and dynamic methods (core floods) were used to determine HPAM retention. There are both advantages and disadvantages associated with determining polymer retention using static tests versus dynamic tests and using aerobic versus anaerobic conditions. From static retention measurements, polymer adsorption values on pure silica sand or Berea sandstone were small, and they showed little difference between experiments conducted aerobically or anaerobically. For both aerobic and anaerobic conditions, HPAM retention increased significantly with increased pyrite or siderite content. Static retention under anaerobic conditions ranged from 45-75 µg/g with 1% of either pyrite or siderite to 137-174 µg/g for 10% pyrite or siderite to 1161-1249 µg/g for 100% pyrite or siderite. If iron minerals are present, the most representative polymer retention results are obtained (for both static and dynamic tests) if conditions are anaerobic. Retention values (from static measurements) under aerobic conditions were commonly twice those determined under anaerobic conditions. If iron minerals are present and retention tests are performed under aerobic conditions, TOC or some similar method should be used for polymer detection. Viscosity detection of polymer may provide retention values that are too high (because oxidative degradation can be misinterpreted as polymer retention). For a broad range of siderite content, retention from static tests did not depend on whether dissolved oxygen was present. However, for a broad range of pyrite content, HPAM retention was significantly lower in the absence of dissolved oxygen than under aerobic conditions. Theses results may be tied to iron solubility. When polymer solutions were mixed with 100% pyrite over the course of 12 hours, 360–480-ppm iron dissolved into polymer solutions under both aerobic and anaerobic conditions, whereas with 100% siderite, only 0–0.6-ppm iron dissolved. If dynamic methods (i.e., corefloods) are used to determine polymer retention under aerobic conditions, flow rates should be representative of the field application. Rates that are too high lead to underestimation of polymer retention. With 10% pyrite, dynamic retention was 211 μg/g at 6 ft/d versus 43.2 μg/g at 30 ft/d. In contrast, retention values were fairly consistent (40.6 – 47.8 μg/g) between 6 ft/d and 33 ft/d under anaerobic conditions.

Clostridium perfringens is the most common cause of gas gangrene (clostridial myonecrosis), a disease that begins when ischaemic tissues become contaminated with C. perfringens vegetative cells or spores. An aerotolerant anaerobe, C. perfringens quickly multiplies in ischaemic tissues and spreads to healthy areas, leading to a high level of morbidity and mortality. As a species, the bacterium can synthesize 13 different toxins, and these are thought to be the major virulence factors of the disease. However, we present evidence here that C. perfringens can also persist inside macrophages, under aerobic conditions, by escaping the phagosome into the cytoplasm. C. perfringens was not killed by the cells of a clone (J774-33) of the macrophage-like murine cell line J774A.1 under aerobic or anaerobic conditions, whereas the non-pathogenic bacterium Bacillus subtilis was killed by J774-33 cells under both conditions. Electron microscopy images showed that C. perfringens cells were intact and resided mostly in the cytoplasm of J774-33 cells, whereas B. subtilis was in the phagosome. Immunofluorescence microscopy showed that intracellular C. perfringens bacteria failed to co-localize with the late endosome-lysosomal marker glycoprotein LAMP-1, whereas B. subtilis did co-localize with LAMP-1. C. perfringens also appeared to escape the phagosome of both activated and unactivated mouse peritoneal macrophages, but not as efficiently as was seen with the J774-33 cell line. In addition, cytochalasin D was used to show that phagocytosis of C. perfringens was dependent on actin polymerization and that the bacteria attach to J774-33 cells at distinct areas of the cell membrane. We propose that the ability to escape the phagosome and persist inside macrophages is an important factor in the early stages of a gangrene infection, when bacterial numbers are low and phagocytic cells are present.

The Impact of O2 on the Fe–S Cluster Biogenesis Requirements of Escherichia coli FNR

Impact of relative air humidity (RAH) and watering mode on responses of cucumber (Cucumis sativus L.) plants to a daily short-term (2 h) temperature decrease to 10oC (DROP treatment) was investigated. Plants were grown at comparably high (80%) or low (30%) RAH under conditions of normal watering or in the mode of artificially created “periodic drought.” It was found that RAH and watering mode exhibit strong quantitative and qualitative influence on plant responses to DROP treatment. Under high RAH, DROP treatment exhibits significant morphogenetic effect increasing plant biomass and compactness. Under the conditions of low RAH, effects of DROP treatment on plant compactness were leveled due to strong morphogenetic effect of the RAH itself and significant decrease in DROP-treated plant biomass under “drought”. Watering mode influenced on the effect of DROP treatment in a different manner depending on RAH. At high RAH, DROP treatment, together with “drought,” led to increase in plant compactness as well as their chilling tolerance. Besides, these plants became more tolerant to water stress induced by low temperature (4°C). At low RAH, no increase in compactness of DROP-treated plants was observed.

Soil aeration is a crucial factor that regulates crop residue decomposition, and the chemical composition of decomposing crop residues may change the forms and availability of soil nutrients, such as N and P. However, to date, differences in the chemical composition of crop straw residues after incorporation into soil and during its decomposition under anaerobic vs. aerobic conditions have not been well documented. The objective of the present study was to assess changes in the C-containing functional groups of wheat straw residue during its decomposition in anaerobic and aerobic environments. A 12-month incubation experiment was carried out to investigate the temporal variations of mass, carbon, and nitrogen loss, as well as changes in the chemical composition of wheat (Triticum aestivum L) straw residues under anaerobic and aerobic conditions by measuring C-containing functional groups using solid state nuclear magnetic resonance (NMR) spectroscopy. The residual mass, carbon content, and nitrogen content of the straw residue sharply declined during the initial 3 months, and then slowly decreased during the last incubation period from 3 to 12 months. The decomposition rate constant (k) for mass loss under aerobic conditions (0.022 d-1) was higher than that under anaerobic conditions (0.014 d-1). The residual mass percentage of cellulose and hemicellulose in the wheat straw gradually declined, whereas that of lignin gradually increased during the entire 12-month incubation period. The NMR spectra of C-containing functional groups in the decomposing straw under both aerobic and anaerobic conditions were similar at the beginning of the incubation as well as at 1 month, 6 months, and 12 months. The main alterations in C-containing functional groups during the decomposition of wheat straw were a decrease in the relative abundances of O-alkyl C and an increase in the relative abundances of alkyl C, aromatic C and COO/N-C = O functional groups. The NMR signals of alkyl C and aromatic C in decomposing wheat straw residues under anaerobic condition were higher than those under aerobic conditions. The higher mass percentages of lignin and the higher signals of aromatic C and alkyl C functional groups in decomposing wheat residues under anaerobic conditions than under aerobic conditions were due to the slower decomposition rates of aryl C and alkyl C in wheat straw residues under anaerobic conditions.

Clostridium perfringens vegetative cells cause both histotoxic infections (e.g., gas gangrene) and diseases originating in the intestines (e.g., hemorrhagic necrotizing enteritis or lethal enterotoxemia). Despite their medical and veterinary importance, the molecular pathogenicity of C. perfringens vegetative cells causing diseases of intestinal origin remains poorly understood. However, C. perfringens beta toxin (CPB) was recently shown to be important when vegetative cells of C. perfringens type C strain CN3685 induce hemorrhagic necrotizing enteritis and lethal enterotoxemia. Additionally, the VirS/VirR two-component regulatory system was found to control CPB production by CN3685 vegetative cells during aerobic infection of cultured enterocyte-like Caco-2 cells. Using an isogenic virR null mutant, the current study now reports that the VirS/VirR system also regulates CN3685 cytotoxicity during infection of Caco-2 cells under anaerobic conditions, as found in the intestines. More importantly, the virR mutant lost the ability to cause hemorrhagic necrotic enteritis in rabbit small intestinal loops. Western blot analyses demonstrated that the VirS/VirR system mediates necrotizing enteritis, at least in part, by controlling in vivo CPB production. In addition, vegetative cells of the isogenic virR null mutant were, relative to wild-type vegetative cells, strongly attenuated in their lethality in a mouse enterotoxemia model. Collectively, these results identify the first regulator of in vivo pathogenicity for C. perfringens vegetative cells causing disease originating in the complex intestinal environment. Since VirS/VirR also mediates histotoxic infections, this two-component regulatory system now assumes a global role in regulating a spectrum of infections caused by C. perfringens vegetative cells.

Antibiotic susceptibility of human gut-derived facultative anaerobic bacteria is different under aerobic versus anaerobic test conditions

<p>Soil enzymes produced by microorganisms and plants are very sensitive to the variations in microclimate, e.g. aeration, and respond quickly to the induced changes. The majority of the enzyme assays are conducted under normal (temperature and air) conditions irrespectively of the origin of the environmental samples. However, it remains unclear how conditions of assays may affect results in anaerobic systems. In the present study, we have clarified this key gap in current methods by measuring the kinetics of phosphatase, β-glucosidase, and leucine aminopeptidase in paddy soil under aerobic and anaerobic conditions by means of a glovebox. Specifically, we quantified V<sub>max</sub> and K<sub>m</sub> in soil from three compartments in a rhizobox (top bulk (2-5 cm), rhizosphere, and bottom bulk (15-18 cm)) during rice growth. We demonstrate that the activities of three tested enzymes were significantly lower under aerobic conditions compared to anaerobic conditions at three consecutive dates of rice growth. Lower V<sub>max</sub> values for phosphatase in top bulk soil and rhizosphere soil and β-glucosidase in top bulk soil, rhizosphere soil, and bottom bulk soil confirmed that aerobic conditions limited enzyme activities. For leucine aminopeptidase, although the difference in V<sub>max</sub> values between anaerobic and aerobic conditions was not significant, the values always increased under anaerobic conditions compared to aerobic conditions. Compared with anaerobic conditions, the K<sub>m</sub> values for phosphatase under aerobic conditions decreased by 10.11-22.78%. The maximum difference in the K<sub>m</sub> values for β-glucosidase and leucine aminopeptidase between aerobic and anaerobic conditions was 30.93% and 40.53%, respectively. We conclude that enzyme activities of samples taken from the anaerobic or low-redox environment have to be assayed under anoxic conditions to avoid 10-40% underestimation (for V<sub>max</sub>) due to suppression by oxygen.</p>

Assessment of Microbial Induced Calcite Precipitation (MICP) in Fine Sand Using Native Microbes under Both Aerobic and Anaerobic Conditions

Fusarium species cause a broad spectrum of infections including superficial infections in healthy people or disseminated infections in immunocompromised patients. Many of these infections have been associated with proteases secreted by fungi to degrade keratin, an important component of the skin and other tissues. Ischemia and abscess are complications associated to the lack of oxygen in severe mycosis caused by Fusarium. However studies of protein degradation by fungi have been done only in aerobic condition. In this study we hypothesized that protease production would be greater in anaerobic than in aerobic condition. 14 Fusarium isolated from environmental samples were grown in Gelatin Media enriched with sodium nitrate to compare their ability to degrade proteins in anaerobic vs. aerobic conditions. Also antibiotic susceptibility was tested using Fluconazole, Itraconazole and Myconazole in aerobic and anaerobic conditions. All fungi tested showed higher Hydrolysis Capacity Index under anaerobic conditions. In aerobic conditions almost all the fungi tested showed similar colony sizes and halo of protein degradation. On other hand, under anaerobic conditions smallest colony sizes exhibited greater halos of protein degradation. Similarly, all fungi tested were more susceptible to antibiotics in anaerobic conditions too. This study showed high protein degradation in anaerobic conditions. Usually fungal contribution to degradation is ignored due to their low presence in environmental or clinical samples under anaerobic conditions. Our results suggest that Fusarium population could have a role or an impact in anaerobic environments such as ischemia or abscess where protein degradation takes place. Future works includes identification of proteins secreted under anaerobic conditions.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Erv1 is a flavin-dependent sulfhydryl oxidase in the mitochondrial intermembrane space (IMS) that functions in the import of cysteine-rich proteins. Redox titrations of recombinant Erv1 showed that it contains three distinct couples with midpoint potentials of -320, -215, and -150 mV. Like all redox-active enzymes, Erv1 requires one or more electron acceptors. We have generated strains with erv1 conditional alleles and employed biochemical and genetic strategies to facilitate identifying redox pathways involving Erv1. Here, we report that Erv1 forms a 1:1 complex with cytochrome c and a reduced Erv1 can transfer electrons directly to the ferric form of the cytochrome. Erv1 also utilized molecular oxygen as an electron acceptor to generate hydrogen peroxide, which is subsequently reduced to water by cytochrome c peroxidase (Ccp1). Oxidized Ccp1 was in turn reduced by the Erv1-reduced cytochrome c. By coupling these pathways, cytochrome c and Ccp1 function efficiently as Erv1-dependent electron acceptors. Thus, we propose that Erv1 utilizes diverse pathways for electron shuttling in the IMS.