Litter Microorganisms Research Articles

Vine leaf decomposition: Feeding preferences and effects of physico-chemical traits of litter on life-history traits of the woodlice Armadillidium vulgare Latreille, 1804

Litter decomposition is a key ecosystem process which is dependent on the litter characteristics and diversity, the decomposer community and activity, and the environmental conditions. We assessed vine leaf decomposition by Armadillidium vulgare (Latreille, 1804), a terrestrial isopod widely distributed and naturally present in vineyards. We compared the decomposition of three grape varieties (Chardonnay, Pinot Noir and Sauvignon) with regular laboratory food (Tilia tomentosa (Moench, 1785)) for seven consecutive weeks. Seven traits were measured on the four litters tested in order to define their importance concerning (i) litter mass loss by the action of microorganisms and isopods (ii) the trophic traits (consumption and assimilation) and (iii) life-history traits (survival and growth) of A. vulgare. Thus, the chemical and physical traits (C/N ratio, tannin and fiber content, thickness) known to influence litter palatability and digestibility for decomposers were determined by standardized methods. In addition, the copper frequently used in viticulture as a fungicide which is potentially responsible for toxic effects on decomposers was measured by ICP-OES after litter mineralization in nitric acid. Our results showed a higher percentage of decomposability by microorganisms in litter with low cellulose content and C/N ratio. Higher isopod consumption and assimilation was found in the litters which is the poorest in tannin, lignin and copper contents. Variation of consumption according to litter was on average 1.5 to 2.7 lower for grape varieties compared to T. tomentosa litter. Assimilation was significantly lower with Pinot Noir than the other litters. To conclude, after seven weeks of experimentation, this study showed that if the growth and survival of woodlice were not affected by inter-varietal differences in vine leaf quality, their role in the decomposition process may be strongly modulated and reduced, especially after consumption of grape variety litters rich in copper, lignin and tannin.

Survival and inactivation kinetics of Salmonella enterica serovar Typhimurium in irradiated and natural poultry litter microcosms.

The use of poultry litter as a biological soil amendment presents a risk for the preharvest contamination of fresh produce by Salmonella. In order to properly assess this risk, it is important to understand the factors influencing the persistence of Salmonella in poultry litter. This research was performed to investigate the influence of indigenous microflora on the survival of Salmonella Typhimurium in poultry litter. Microcosms of irradiated (sterilized) and natural poultry litter were inoculated with S. Typhimurium, adjusted to pH 8.0, 0.92 water activity (aw), and stored at 30°C for 6 days. S. Typhimurium populations (log CFU g-1) declined in both litter treatments and there were no significant differences (P > 0.05) in recovery between litter treatments on any sampling days (0 to 6). The pH of the natural litter significantly increased (P < 0.05) from 8.42 on day 0 to 9.00 on day 6. By day 6, S. Typhimurium populations in both litter treatments fell below the limit of detection (1 log CFU g-1). The inactivation kinetics of S. Typhimurium in both litter treatments were described by the Weibull model. Under the experimental conditions (pH 8.0, 0.92 aw, 30°C), the presence or absence of poultry litter microflora did not significantly influence the survival of S. Typhimurium. This study demonstrates that the mere presence of poultry litter microflora will not inhibit Salmonella survival. Instead, inhibitory interactions between various microorganisms in litter and Salmonella are likely dependent on more favorable environmental conditions (e.g., aw, pH) for growth and competition.

POPULATION DYNAMICS OF THE MICROBIOTA IN THE LITTER OF TWO TREE SPECIES OF THE ATLANTIC FOREST

This study analyzes microbiota population dynamics as a function of nutrient release rate during litter decomposition. For that, we observed two tree species native to the Atlantic Forest: brazilwood (Paubrasilia echinata) and inga (Inga laurina). To assess nitrogen (N), phosphorus (P), and potassium (K) release rates from the litter, we performed six collections over 365 days. In these collections, we placed polyvinyl bags called ‘litter bags’ below the treetops of the chosen species to collect dry leaves. To identify the groups of litter microorganisms (fungi, bacteria, and actinomycetes), we used the plate culture method to count the number of colony-forming units (CFU), and the fatty acid profile method, through biomarkers, associating nutrient release rate and abiotic factors (temperature and rainfall). Nutrient release rate correlates with litter decomposition at 140 days, and most microorganisms correlate with litter decomposition at 30 days. Nitrogen and phosphorus release rates correlate with rainfall. Fungi correlate with P release rate in inga litter decomposition. The bacteria biomarker 17:1 was the only one that correlated with N and P release rates. In conclusion, rainfall affects nutrient solubilization in the studied species, and microbiota differs between the species. When comparing the two methods to identify these microorganisms, information from one method complements information from the other, since both provide different but interdependent data.

Deprivation of root-derived resources affects microbial biomass but not community structure in litter and soil.

The input of plant leaf litter has been assumed to be the most important resource for soil organisms of forest ecosystems, but there is increasing evidence that root-derived resources may be more important. By trenching roots of trees in deciduous and coniferous forests, we cut-off the input of root-derived resources and investigated the response of microorganisms using substrate-induced respiration and phospholipid fatty acid (PLFA) analysis. After one and three years, root trenching strongly decreased microbial biomass and concentrations of PLFAs by about 20%, but the microbial community structure was little affected and the effects were similar in deciduous and coniferous forests. However, the reduction in microbial biomass varied between regions and was more pronounced in forests on limestone soils (Hainich) than in those on sandy soils (Schorfheide). Trenching also reduced microbial biomass in the litter layer but only in the Hainich after one year, whereas fungal and bacterial marker PLFAs as well as the fungal-to-plant marker ratio in litter were reduced in the Schorfheide both after one and three years. The pronounced differences between forests of the two regions suggest that root-derived resources are more important in fueling soil microorganisms of base-rich forests characterized by mull humus than in forests poor in base cations characterized by moder soils. The reduction in microbial biomass and changes in microbial community characteristics in the litter layer suggests that litter microorganisms do not exclusively rely on resources from decomposing litter but also from roots, i.e. from resources based on labile recently fixed carbon. Our results suggest that both bacteria and fungi heavily depend on root-derived resources with both suffering to a similar extent to deprivation of these resources. Further, the results indicate that the community structure of microorganisms is remarkably resistant to changes in resource supply and adapts quickly to new conditions irrespective of tree species composition and forest management.

Dynamics of Litter Carbon and Nitrogen in Forest Fallows following Shifting Cultivation in Mizoram, Northeast India

In this study, a field trial was carried out on organic matter, carbon (C) and nitrogen (N) dynamics of different litter components (i.e. leaf, branch, roots less than 2 mm and 2-5 mm) in forest fallows (3 years: FL-3, 5 years: FL-5 and 10 years: FL-10) at Muallungthu, Mizoram using litter bag techniques. The rate of organic matter loss and release of C and N was faster in leaf and fine root (less than 2 mm) compared to branch and coarse roots (2-5 mm). Further, litter mass loss rate was higher in longer fallow (FL-10) compared to shorter fallow (FL-3 and FL-5). Results showed that mass loss and release of C and N was largely depending on the initial litter quality, abiotic variables and litter microorganisms. Release of C followed the patter similar to that of mass loss, whereas, N release showed an initial release followed by a slow release or marginal increase that indicate the tendency of N immobilization. Results indicate that the addition of litter from the adjoining forest adds organic matter, C and N in shifting cultivation that may help in sustaining soil fertility and crop productivity of shifting agriculture sites in northeastern hill regions of Mizoram.

Within-House Spatial Distribution of Fecal Indicator Bacteria in Poultry Litter.

Land application of poultry litter is often considered to be a major source of water pollutants in poultry-producing regions. However, reported levels of fecal indicator microorganisms in litter vary widely, with considerable variation possible within houses and across farms, depending on management practices. Therefore, a study was conducted to determine the levels and distribution of indicator microorganisms within 12 broiler farms representing three companies. Within each house, litter samples were collected from around the feed line, water line, north wall, cool pad end, middle, and fan end. Litter moisture content was significantly different within the houses, with the litter being driest around the feed line (19.8%) and wettest around the water line (40.7%). Mean levels of total coliforms, , enterococci, and were 3.7, 3.3, 6.4, and 4.0 log colony-forming units g dry litter, respectively. Levels of total coliforms, , and were positively correlated with litter moisture content, but enterococci levels were not. Consequently, levels of total coliforms, , and , as well as enterococci, were highest around the water line and lowest around the feed line. These results indicate that areas with higher litter water content are more likely to contain higher levels of most fecal indicator microorganisms. Approaches to reduce litter water content in these areas would not only benefit the microbial quality of litter for land application but would also likely improve in-house disease control.

Temporal variation overshadows the response of leaf litter microbial communities to simulated global change

Bacteria and fungi drive the decomposition of dead plant biomass (litter), an important step in the terrestrial carbon cycle. Here we investigate the sensitivity of litter microbial communities to simulated global change (drought and nitrogen addition) in a California annual grassland. Using 16S and 28S rDNA amplicon pyrosequencing, we quantify the response of the bacterial and fungal communities to the treatments and compare these results to background, temporal (seasonal and interannual) variability of the communities. We found that the drought and nitrogen treatments both had significant effects on microbial community composition, explaining 2-6% of total compositional variation. However, microbial composition was even more strongly influenced by seasonal and annual variation (explaining 14-39%). The response of microbial composition to drought varied by season, while the effect of the nitrogen addition treatment was constant through time. These compositional responses were similar in magnitude to those seen in microbial enzyme activities and the surrounding plant community, but did not correspond to a consistent effect on leaf litter decomposition rate. Overall, these patterns indicate that, in this ecosystem, temporal variability in the composition of leaf litter microorganisms largely surpasses that expected in a short-term global change experiment. Thus, as for plant communities, future microbial communities will likely be determined by the interplay between rapid, local background variability and slower, global changes.

Trophic niche differentiation and utilisation of food resources in collembolans based on complementary analyses of fatty acids and stable isotopes

Feeding on a variety of resources, collembolans have been assumed to be food generalists. However, recent stable isotope analyses documented that collembolan species occupy different trophic levels, but detailed studies on species-specific food resources are sparse. Further, it still is little understood whether food resources of collembolan species are constant or shift, e.g., with habitats. Fatty acid (FA) and stable isotope analysis allow insight into utilisation of basal resources and trophic levels of consumers, respectively. We combined these methods to investigate variations in trophic niches of six collembolan species (Lepidocyrtus lanuginosus, Folsomia quadrioculata, Parisotoma notabilis, Ceratophysella denticulata, Isotomiella minor and Protaphorura armata) in beech and spruce forests. We correlated collembolan FAs with that of litter microorganisms at the respective study sites to identify links to resources. FA composition and stable isotope signatures in collembolan species did not differ significantly between forest types but between species suggesting pronounced trophic niche differentiation between species. The trophic niche of C. denticulata and P. armata was similar and significantly differed from the other species with 13C and 15N signatures being least depleted. We suggest that C. denticulata has a predatory life style feeding on nematodes. Due to intermediate to low 13C and 15N levels and specific FA compositions the other collembolan species could be ascribed to secondary decomposers with I. minor being more closely associated with bacterial resources and F. quadrioculata, L. lanuginosus and P. notabilis with fungal resources. However, dietary niches presumably comprise a mixture of resources rather than single resources. FAs in collembolan species correlated poorly with those in litter suggesting that the diet of collembolan species is rather independent of the structure of microbial communities in bulk litter. The results suggest that collembolans consume resources of microsites rather than bulk material thereby benefitting from the small-scale heterogeneity in resource distribution in soil. Low variation in trophic niches with forest type suggests that these microsites are similar across different forests and provide similar food resources despite marked differences in e.g., litter materials and humus structure.

Influence of urea on the cherry leaf spot pathogen, Blumeriella jaapii, and on microorganisms in decomposing cherry leaves

Growth chamber and orchard experiments were carried out to clarify the response of the cherry leaf spot pathogen, Blumeriella jaapii, and microorganisms in the leaf litter to two levels of urea (2.5% or 5%) applied post leaf fall to sour cherry leaves. In general, urea application reduced the development of B. jaapii measured as biomass by quantitative PTA-ELISA in the leaf litter and spore counting in the spring and increased the overall microbial biomass (measured with biomarker phospholipid fatty acids (PLFAs)) and fungal activity (assessed as β- N-acetylglucosaminidase activity). The biomass increase of all groups of microorganisms in the litter generally began immediately after application of urea and, with the notable excepts of B. jaapii and Gram-negative bacteria containing the biomarker PLFA cyclo17:0, continued after the ammonia and pH levels had stabilized to levels similar to the control leaves approximately 10 days later. Application of 2.5% urea increased the biomass of most groups of saprotrophic microorganisms and accelerated litter decomposition to a higher extent than application of 5% urea and during the first week after treatment applications the 5% urea level inhibited the total microbial biomass. This may be ascribed to ammonia toxicity as 5% urea resulted in a markedly higher ammonia elevation than 2.5% urea, the first week after application. From then onwards in both the 2.5% and 5% treatments the fungal and Gram-positive communities benefited from a lowered C:N ratio, increasing their activities approximately 2 times compared to a water-treated control. Inhibition of B. jaapii coincided with the period of urea breakdown in which elevated levels of ammonia and leaf pH were measured in the treated leaves. This period lasted for approximately 10 days after which the biomass of B. jaapii in the treated leaves continued to decrease at a slow but faster rate than in the untreated leaves. Our results indicate that the urea application caused an elevation in leaf pH and ammonia levels, which together with an acceleration in litter decomposition, adversely affected the saprotrophic growth of B. jaapii, leading to reduced production of ascospores and winter-conidia the following spring.

Nutritional deprivation increases intracellular phosphate and polyphosphate in poultry litter microflora

To determine if mixed microflora from poultry litter accumulates phosphate when deprived of carbon and energy or nitrogen sources. Microbial enrichments from poultry litter capable of metabolizing ammonia, amino acids, and glucose were subjected to nutritional deprivation and the effects on intracellular phosphate levels were determined. Results indicate deprivation of glucose yields a 38 and 50% increase in intracellular phosphate and polyphosphate levels, respectively. Deprivation of nitrogen sources did not result in significant intracellular phosphate accumulation. Micro-organisms normally present in poultry litter respond to carbohydrate deprivation by accumulating intracellular phosphate. Poultry litter typically contains significant levels of phosphate which contribute to environmental pollution when applied to land. Phosphate is highly mobile in soils and often drains into local watersheds following rain events. This study raises the possibility that poultry litter micro-organisms may have the capacity to sequester phosphate, which could delay or diminish phosphate run-off.

Annual dynamics of phosphatase activities in an evergreen oak litter: influence of biotic and abiotic factors

As part of a study of the processes involved in litter biodegradation, we considered the variations over 1 year of the phosphatase activities in sclerophyllous evergreen oak litter ( Quercus ilex L.). Evergreen oak is representative of tree species in the forests of the French Mediterranean area. Acid (E.C. 3.1.3.2.) and alkaline (E.C. 3.1.3.1.) phosphatases, were measured over 13 months in the forest litter, along with several biotic and abiotic variables, potentially involved in the regulation of these enzymes. These comprised moisture, temperature, pH, water-extractable inorganic P (P I), fungi, culturable heterotrophic bacteria and protein concentrations. Moisture considerably affected the production of proteins and acid phosphatases, probably formed by litter microorganisms. This result corroborated the study of Criquet et al. [Soil Biology and Biochemistry 34 (2002) 1111] which indicated that rainfall was the most important factor regulating the production and the activity of numerous enzymes in sclerophyllous forest litter. However, it appeared that moisture cannot alone predict all of the variations in phosphatase activities and the mineralisation rate of organic P (P O). Indeed, principal component analyses (PCA) and multiple regressions showed that temperature and bacterial communities were also implicated in phosphatase dynamics and P O mineralisation. Acid phosphatases were negatively correlated with the temperature, whilst alkaline phosphatases were positively correlated with this variable. The significant correlation obtained between bacteria and P I concentrations, and the lack of correlation between bacteria and both acid and alkaline phosphomonoesterases, suggest that other important phosphatase types, such as phosphodiesterases, must be strongly implicated in P O mineralisation of the litter and in the regulation of P microbial metabolism.

Bioaccumulation and biosorption of lead by poultry litter microorganisms

Microorganisms are known to interact with metals through a number of mechanisms, including binding the metals to their cells' walls and intracellular accumulation. Poultry litter has a high density of various microorganisms along with many nutrients. The objective of this research was to study the removal of Pb from an aqueous solution by the microorganisms found in poultry litter under an aerobic environment. A Pb(NO3)2 solution was treated with the aqueous extract of either the nonradiated litter or gamma-radiated litter in order to differentiate between the removal of Pb through bioaccumulation (by the living organisms) and biosorption (by the dead organisms). Lead removal was measured using anodic stripping voltammetry. Both the nonradiated and the gamma-radiated litter removed significant amounts of Pb. After 14 d, the amount of Pb removed through bioaccumulation by the nonradiated litter and through biosorption by the radiated litter was about 44 and 30%, respectively. There was no increase in Pb removal between 14 and 60 d. The biomass density of the aqueous extract of poultry litter increased significantly in the presence of 400 ppb Pb(NO3)2.

Biodegradation of phenol with poultry litter microorganisms

This study was undertaken to measure the aerobic biodegradation of phenol using poultry litter and to compare the toxicity of the parent compound with the end product(s). Phenol was aerobically treated with a water extract of the untreated litter or of irradiated litter in order to differentiate between the effects of the microorganisms and other chemical species present in the litter on the biodegradation of phenol. Two concentrations of phenol (10 ppm and 100 ppm) were each treated with three concentrations of leachate (0.2%, 0.5% and 1%). The litter leachate (1%) degraded 10 ppm and 100 ppm phenol by 88% in 8 h and 24 h, respectively. Lag phases were observed for all treatments except with 1% leachate. The lag phase increased as the concentration of phenol increased and decreased with an increase in the leachate concentration. No degradation was observed using the leachate of the irradiated litter. Experiments using Ceriodaphnia dubia, (LD50) and Vibrio fischeri, (EC50) showed that the degradation end product (s) were non‐toxic compared with the parent compound.