Direct and indirect effects of low pH on the transformation of detrital energy by the shredding caddisfly, Clistoronia magnifica (Banks) (Limnephilidae)

1985 ◽  
Vol 63 (10) ◽  
pp. 2298-2304 ◽  
Author(s):  
K. van Frankenhuyzen ◽  
G. H. Geen ◽  
C. Koivisto
Keyword(s):  
Leaf Litter ◽  
Indirect Effects ◽  
Food Resource ◽  
Larval Survival ◽  
Low Ph ◽  
Late Instar ◽  
Early Instar ◽  
Acidic Conditions ◽  
Accelerated Growth

A shredding caddisfly, Clistoronia magnifica (Banks), was used to test the hypotheses that increased acidity would reduce the transformation of detrital energy into shredder biomass by (i) reducing survival, (ii) increasing maintenance costs at the expense of growth, and (iii) reducing food quality as a result of inhibition of microbial activity on the leaf litter. Low pH reduced larval survival immediately after hatching and during the moult from third to fourth instar. However, surviving larvae developed faster at pH 4.2–5.2 than at pH 5.8–6.4 and produced larger pupae and adults. Low pH did not alter metabolic costs or ingestion rates of fourth- and fifth-instar larvae. Accelerated growth resulted from indirect effects of low pH on the food resource, which suggested improved nutritional quality of leaf litter conditioned at low pH. However, enhanced growth of late instar larvae did not compensate for reduced survival of early instar larvae, possibly resulting in lower shredder production under acidic conditions.

Microbe-mediated effects of low pH on availability of detrital energy to a shredder, Clistoronia magnifica (Trichoptera: Limnephilidae)

1986 ◽  
Vol 64 (2) ◽  
pp. 421-426 ◽  
Author(s):  
K. van Frankenhuyzen ◽  
G. H. Geen
Keyword(s):  
Nutritional Quality ◽  
Fungal Biomass ◽  
Bacterial Abundance ◽  
Larval Growth ◽  
Low Ph ◽  
Microbial Colonization ◽  
Fungal Enzymes ◽  
Mediated Effects ◽  
Late Instar

We tested the hypothesis that microbe-mediated changes in nutritional quality of leaf litter conditioned at low pH enhanced larval growth of the caddisfly shredder Clistoronia magnifica. Alder leaves conditioned for more than 3 weeks at pH 4 had greater fungal biomass and bacterial abundance than leaves conditioned at pH 6. Differential microbial colonization did not affect ingestion rates. Radioisotope experiments indicated that late-instar larvae assimilated microbe-derived energy from leaves conditioned at pH 4 with a 10–15% higher efficiency than microbial energy from leaves conditioned at pH 6 and suggested a concomitant 5% increase in assimilation of leaf-derived energy. Enhanced growth of C. magnifica at low pH could be accounted for by increased fungal biomass on leaves conditioned at low pH and increased availability of leaf energy, presumably due to additional modification of the leaf substrate by fungal enzymes.

Direct and Indirect Effects of Crisaborole Ointment on Quality of Life in Patients with Atopic Dermatitis: A Mediation Analysis

2017 ◽  
Vol 1 ◽  
pp. s36
Author(s):  
Eric Simpson ◽  
Andrew Bushmakin ◽  
Joseph C Cappelleri ◽  
Thomas Luger ◽  
Sonja Stander ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Atopic Dermatitis ◽  
Mediation Analysis ◽  
Indirect Effects ◽  
Direct And Indirect Effects

Abstract Not Available

Venturia pirina. [Descriptions of Fungi and Bacteria].

1974 ◽  
Author(s):  
A. Sivanesan
Keyword(s):  
Leaf Litter ◽  
Geographical Distribution ◽  
Primary Infection ◽  
Secondary Infection ◽  
Apple Scab ◽  
Black Spot ◽  
Eriobotrya Japonica ◽  
Venturia Pirina ◽  
Young Growth

Abstract A description is provided for Venturia pirina. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Principally on pear (Pyrus communis) and other Pyrus spp., also recorded from Eriobotrya japonica (loquat) (Herb. IMI). DISEASE: Causes scab or black spot of pear, which results in loss of quantity and quality of fruit. The disease attacks shoots, buds, leaves and fruit, symptoms and aetiology being very similar to those of apple scab caused by V. inaequalis on Malus spp. (CMI Descript. 401). Dark, more or less circular scabs are produced on leaves and fruit, often with some growth distortion. Infection of young wood is more common than with apple scab and causes pale brown blister-like lesions which burst to release conidia in the following year. GEOGRAPHICAL DISTRIBUTION: Worldwide in temperate and subtropical regions wherever pears are grown (see CMI Map 367, ed. 2, 1968). TRANSMISSION: Epidemiology is similar to that of apple scab. The overwintering saprophytic perithecial stage on leaf litter releases airborne ascospores in spring which infect young growth, and secondary infection by conidia dispersed during wet summer weather also occurs. Overwintering lesions on young wood are more frequent than with apple scab and conidia produced by these in the spring can be an important source of primary infection (46, 2061; 47, 849).

Microbial Quality of Hoummos (Chickpea Dip) Commercially Produced in Jordan

1994 ◽  
Vol 57 (5) ◽  
pp. 431-435 ◽  
Author(s):  
MOHAMMED I. YAMANI ◽  
BASIM A. AL-DABABSEH
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Low Ph ◽  
Plate Count ◽  
Microbial Quality ◽  
Aerobic Plate Count ◽  
And Staphylococcus Aureus ◽  
Reference Samples ◽  
Hygienic Conditions

Sixty samples of fresh hoummos (chickpea dip) from 15 restaurants were examined in winter and summer to find out numbers and types of microorganisms present. Five reference samples, produced by the investigators under hygienic conditions, were examined for comparison. The microbial load of commercial hoummos was high, and spherical lactic acid bacteria (LAB) belonging to Lactococcus, Enterococcus and Leuconostoc were the predominant microorganisms. The means of the aerobic plate count (APC) and the counts of LAB and coliforms (1.9 × 108, 1.6 × 108 and 2.9 × 105/g, respectively) in summer samples were significantly higher (p < 0.05) than the averages of the same counts in winter samples (2.7 × 107, 1.6 × 107 and 2.2 × 103/g). The average summer and winter yeast counts were 4.2 × 104 and 1.5 × 104g, respectively. In reference samples of hoummos, APC and LAB counts were < 103/g, while the coliform and yeast counts were < 10/g and 102/g, respectively, indicating lack of hygienic practices during the production of commercial hoummos. Salmonella was not detected in any sample, and Escherichia coli and Staphylococcus aureus counts of all samples were < 10/g. The relatively low pH of hoummos (the average pH of all samples was 5.1) and the rapid growth of LAB, possibly accompanied by production of inhibitory substances, may explain the predominance of these bacteria, and could have contributed to the absence of the pathogens examined.

scholarly journals AguR Is Required for Induction of the Streptococcus mutans Agmatine Deiminase System by Low pH and Agmatine

2009 ◽  
Vol 75 (9) ◽  
pp. 2629-2637 ◽  
Author(s):  
Yaling Liu ◽  
Lin Zeng ◽  
Robert A. Burne
Keyword(s):  
Gene Expression ◽  
Dna Binding ◽  
Streptococcus Mutans ◽  
Low Ph ◽  
Binding Domain ◽  
Negative Regulator ◽  
Dna Binding Domain ◽  
Mutant Proteins ◽  
Acidic Conditions ◽  
Agmatine Deiminase

ABSTRACT Acidic conditions and the presence of exogenous agmatine are required to achieve maximal expression of the agmatine deiminase system (AgDS) of Streptococcus mutans. Here we demonstrate that the transcriptional activator of the AgDS, AguR, is required for the responses to agmatine and to low pH. Linker scanning mutagenesis was used to create a panel of mutated aguR genes that were utilized to complement an aguR deletion mutant of S. mutans. The level of production of the mutant proteins was shown to be comparable to that of the wild-type AguR protein. Mutations in the predicted DNA binding domain of AguR eliminated activation of the agu operon. Insertions into the region connecting the DNA binding domain to the predicted extracellular and transmembrane domains were well tolerated. In contrast, a variety of mutants were isolated that had a diminished capacity to respond to low pH but retained the ability to activate AgDS gene expression in response to agmatine, and vice versa. Also, a number of mutants were unable to respond to either agmatine or low pH. AguD, which is a predicted agmatine-putrescine antiporter, was found to be a negative regulator of AgDS gene expression in the absence of exogenous agmatine but was not required for low-pH induction of the AgDS genes. This study reveals that the control of AgDS gene expression by both agmatine and low pH is coordinated through the AguR protein and begins to identify domains of the protein involved in sensing and signaling.

Annual differences in quality of leaf litter of aspen (Populus tremuloides) affecting rates of decomposition

1988 ◽  
Vol 66 (10) ◽  
pp. 1940-1947 ◽  
Author(s):  
Barry R. Taylor ◽  
Dennis Parkinson
Keyword(s):  
Water Absorption ◽  
Leaf Litter ◽  
Populus Tremuloides ◽  
Decomposition Rate ◽  
Rocky Mountains ◽  
Absorption Rate ◽  
Trembling Aspen ◽  
Leaching Loss ◽  
The Difference

Freshly fallen leaf litter was collected from a stand of trembling aspen (Populus tremuloides Michx.) in the Rocky Mountains of Alberta each autumn from 1981 through 1984. Leaves from 1981 and 1982 were yellow, waxy, and strong. Leaves from 1983 were pale brown and very brittle, and almost 1% of them suffered symmetrical deformities. Leaves from 1984 were composed of 80% yellow leaves and 20% green leaves, which apparently abscissed before senescence. Green and yellow 1984 leaves were distinctly different with respect to total (3 days) leaching loss, leachate conductivity, and proportions of ash, cellulose, and labile material. Green 1984 leaves contained twice as much nitrogen as yellow ones (13.1 vs. 6.5 mg∙g−1) and significantly more phosphorus (1.6 vs. 1.3 mg∙g−1). Leaves of different years varied widely with respect to leaf mass, water absorption rate, mass and conductivity of leachate, and proportions of cellulose, labiles, lignin, and ash, but there was no consistent ordering among years; leaves of different colouration (especially 1981 and 1983) were often physicochemically similar, while leaves identical in appearance were often chemically different. Small but significant differences in N and P concentrations among years were removed by 2 h leaching. Leaves of 1981 decomposing in laboratory microcosms at 26 °C lost less mass than either 1982 or 1983 leaves after 1 month, but not after 2 months. Ability of the cuticle to resist water absorption was probably responsible for the difference in initial decomposition rate.

Development of Toxic Degradation Products during Heat Sterilization of Glucose-Containing Fluids for Peritoneal Dialysis: Influence of Time and Temperature

1995 ◽  
Vol 15 (1) ◽  
pp. 26-32 ◽  
Author(s):  
Per Kjellstrand ◽  
Evi Martinson ◽  
Anders Wieslander ◽  
Björn Holmquist
Keyword(s):  
Peritoneal Dialysis ◽  
Glucose Solution ◽  
Degradation Products ◽  
General Pattern ◽  
Low Ph ◽  
Uv Absorbance ◽  
Influence Of Temperature ◽  
In Vitro Systems

Objective Fluids for peritoneal dialysis (PD) cause cytotoxic reactions in many different in vitro systems. The low pH, the high osmolality of the fluids, and the glucose degradation products formed during heat sterilization have been considered responsible. In the present study, we investigate the influence of temperature and time during heat sterilization of PD fluids and glucose solutions on glucose degradation and cytotoxicity of the solutions. Design Ampoules containing PD-fluid or glucose solution were heated in an oil bath to predetermined F o values (combinations of time and temperature giving equal energy/bacteriallethality). Cytotoxicity of the solutions was measured as groWth inhibition of cultured L-929 fibroblasts. Glucose degradation was measured as UV absorbance at 228 and 284 nm. Results The same general pattern was seen in both PD fluid and glucose solution. Cytotoxicity decreased from 90% to 15% when the sterilization temperature was increased from 115° to 140°C and concomitantly the length of time shortened in order to maintain equal bacteriallethality. Under the same conditions, degradation products, measured as UV absorbance at 284 nm, decreased from 0.2 to 0.02. Conclusion To minimizethe development of cytotoxic breakdown products, high temperatures over short periods of time should be used to heat-sterilize PD fluids. Even as small an increase as 5°C at around 120°C will improve the quality of the solutions.

Application of Methanobrevibacter acididurans in anaerobic digestion

2004 ◽  
Vol 50 (6) ◽  
pp. 109-114 ◽  
Author(s):  
D.V. Savant ◽  
D.R. Ranade
Keyword(s):  
Fatty Acids ◽  
Anaerobic Digestion ◽  
Methane Production ◽  
Volatile Fatty Acids ◽  
Low Ph ◽  
Anaerobic Digesters ◽  
Hydrogenotrophic Methanogen ◽  
Distillery Wastewater ◽  
Acid Tolerant ◽  
Acidic Conditions

To operate anaerobic digesters successfully under acidic conditions, hydrogen utilizing methanogens which can grow efficiently at low pH and tolerate high volatile fatty acids (VFA) are desirable. An acid tolerant hydrogenotrophic methanogen viz. Methanobrevibacter acididurans isolated from slurry of an anaerobic digester running on alcohol distillery wastewater has been described earlier by this lab. This organism could grow optimally at pH 6.0. In the experiments reported herein, M. acididurans showed better methanogenesis under acidic conditions with high VFA, particularly acetate, than Methanobacterium bryantii, a common hydrogenotrophic inhabitant of anaerobic digesters. Addition of M. acididurans culture to digesting slurry of acidogenic as well as methanogenic digesters running on distillery wastewater showed increase in methane production and decrease in accumulation of volatile fatty acids. The results proved the feasibility of application of M. acididurans in anaerobic digesters.

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