alvi, of the stomach, of the digestive organs) Cells are Gram-po

alvi, of the stomach, of the digestive organs). Cells are Gram-positive, nonmotile, nonspore-forming, short-rod-shaped and catalase-negative. Growth occurs under aerobic and anaerobic conditions. Colonies are white, irregular, and convex

when grown on MRS agar under aerobic conditions for 48 h. Better growth is obtained at 40 than 37 °C. The DNA G+C content is 42.7 mol%. Acid is produced from ribose, galactose, d-glucose, d-mannose, maltose, lactose, melibiose, sucrose, and d-raffinose. No acid is produced from glycerol, erythritol, d- and l-arabinose, d- and l-xylose, adonitol, β-methyl-d-xyloside, d-fructose, l-sorbose, rhamnose, dulcitol, inositol, mannitol, sorbitol, α-methyl-d-mannoside, α-methyl-d-glucoside, N-acetyl-glucosamine, amygdalin, arbutin, esculin, salicin, cellobiose, trehalose, inulin, melezitose, BMS-354825 chemical structure amygdalin, glycogen, xylitol, β-gentiobiose, d-turanose, d-lyxose, d-tagatose, d- and l-fucose, d- and l-arabitol, gluconate, 2-keto-gluconate and 5-keto-gluconate. The strain is heterofermentative and produces dl-lactic acid from glucose. The predominant cellular fatty acids are C18:1 ω9c and C16:0. The type strain, R54T (=KCCM 90099T = JCM 17644T), was isolated from the gizzard

of hens. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and click here Technology (2009-0090020). We also thank Dr J. P. Euzéby for suggestions regarding nomenclature. The GenBank accession number for the 16S rRNA gene sequence of strain R54T is HQ718585. “
“The gyrase mutations and efflux pumps confer fluoroquinolones (FQ) resistance in Mycobacterium tuberculosis. However, the contribution of two mechanisms in FQ mono-resistant M. tuberculosis is still unclear. Here, we investigated the contribution of gyrase mutations and efflux pumps to FQ resistance among 17 clinical FQ mono-resistant strains. Our data showed that gyrase mutations in gyrA QRDR selleck were only responsible for four FQ mono-resistant strains. Mutations located in Ala90 and Asp94

of GyrA confer high-level LFX resistance, which can be explained by 3D modeling affinity change between GyrA and LFX. In addition, we found that a high level of efflux pump pstB transcripts may confer FQ resistance in two high-level FQ-resistant isolates (MIC ≥ 4 μg mL−1). The recombinant Escherichia coli with pstB revealed greatly increased MIC level from < 0.125 μg mL−1 to 2 μg mL−1. For the two isolates harboring high-level pstB transcripts, the presence of CCCP reduced LFX resistance to 1.0 μg mL−1. The transcriptional levels of pstB showed no significant difference among 10 clinical M. tuberculosis isolates with different drug susceptibility profiles. In conclusion, our findings demonstrate that both QRDR mutation and efflux pump mechanisms are responsible for monoresistance to FQ. PstB may serve as FQ-related efflux pumps in M. tuberculosis.

It is important for HRM analysis to select the proper length of P

It is important for HRM analysis to select the proper length of PCR product. We compared different lengths of PCR product and evaluated the effect of length on the reaction’s sensitivity (data not

shown). The shorter PCR fragment was more sensitive for identification of differences in DNA sequence than the long one used as the reference (Rizvi & Bej, 2010). Also, the PCR should be optimized for making Ct values between 15 and 35, in order for the specific sigmoid-shaped curve for reliable HRM data to be exhibited (Winchell et al., 2010). The tmRNA coded by the ssrA gene is present in high copy numbers in the cell (Schonhuber et al., 2001), so it was easy to solve the problem, as shown in Fig. 2a. No currently available assays using the HRM

technique check details are known to identify Listeria species. O’Grady et al. (2008) described a fluorescence resonance energy transfer (FRET) hybridization probe Q-PCR assay combined with melting peak analysis to detect BAY 57-1293 chemical structure L. monocytogenes and identify five classical Listeria species. Even though the assay showed a promising performance, all classical Listeria species could not be identified completely. The assay developed here could identify six classical Listeria species, and L. ivanovii was separated from L. seeligeri because of only two different bases (Fig. 1). This approach was applied to correctly identify 53 Listeria species and 45 non-Listeria species to testify to its reliability. The results showed that distinctive HRM profiles could be generated, and after many experiments, the Tm values specific to each species were replicable among the isolates and standard strains of the same species. Thirty artificially contaminated food samples were detected, and only two of these could not be identified. The sensitivity of artificially contaminated samples was 102 CFU mL−1. Thus, the reason may be that the sample concentrations did not reach the LLOD. When the assay is performed in another

Histamine H2 receptor laboratory on the different Q-PCR instrument, we suggest that the standard strains or positive plasmids corresponding to the six Listeria species are needed as positive controls for calibration. Deviations in Tm values may appear from those reported here, but will not have an impact on the final results because analysis will rest on the DNA sequence of the controls. We employed Q-PCR integrated with HRM analysis to develop an assay for rapid identification of six Listeria species by targeting the ssrA gene at the species level. The validity of the assay was confirmed in 30 artificially contaminated food samples. We will further evaluate the validity of this assay in real clinical and food samples as others did (Wolff et al., 2008; Mitchell et al., 2009; Pietzka et al., 2009). This assay should be a useful alternative for identification of Listeria species, effectively complementing current procedures in clinical diagnostics and food safety, and saving time and expense.

Comparing amino acid identities between 11 TcAAAP analysed, TcAAA

Comparing amino acid identities between 11 TcAAAP analysed, TcAAAP411 is located close to TcAAAP545 in the identity-based phenogram (Fig. 2b). These data correlate perfectly with in vitro results where both genes were capable of reversing canavanine resistance in yeasts. However, the Leishmania donovani arginine permease LdAAP3 (Shaked-Mishan et al., 2006) is located in a branch distant from TcAAAP411. In silico topological analysis of TcAAAP411 using TMpred (http://www.ch.embnet.org/software/TMPRED_form.html) predicted 10 transmembrane helices and the variable N-terminal domain outside the cell. Two copies of TcAAAP411 were found in the T. cruzi genome database

(GeneDB, http://www.genedb.org/), one characterized

herein, and the other haplotype with three different amino acid positions (GeneDB systematic ID: Sirolimus Tc00.1047053506053.10). To define the substrate specificity of the permease, competitive transport studies were undertaken. The initial rate of arginine uptake was measured in the presence of 20 μM arginine and 20-fold excess of unlabelled competing molecule. selleck Considering the participation of other endogenous yeast amino acid permeases, control experiments were also performed using pDR196 yeasts. None of the tested compounds produced a significant decrease on arginine uptake except unlabelled arginine, as expected (Fig. 2c). To test whether canavanine can enter the cells through TcAAAP411, as occurs in the selection yeast media, the same assay fantofarone was repeated using a 50-fold excess of canavanine. The inset in Fig. 2c shows that, in these conditions, canavanine produced a significant decrease on arginine uptake of about 50%. Transport of l-arginine by TcAAAP411 yeasts was found to be roughly proportional to an incubation time up to 20 min (Fig. 2d, inset). Data obtained from concentration-dependent arginine influx curves were analysed using Lineweaver–Burk plots and the apparent Michaelis–Menten constant (Km) value was estimated as about 30 μM (Fig. 2d).

Ten years ago, T. cruzi arginine transport, coupled to phosphoarginine synthesis, was identified and biochemically characterized (Pereira et al., 1999). This transport system showed very similar kinetic parameters and substrate specificity to TcAAAP411, suggesting that this permease is at least one component of the previously measured arginine transport system. Recently, a similar arginine transporter (LdAAP3) has been identified in the protozoan parasite L. donovani (Shaked-Mishan et al., 2006). Its regulation depends on the availability of the extracellular substrate, as amino acid starvation produces an increase in arginine transport and LdAAP3 abundance (Darlyuk et al., 2009). Interestingly, this mechanism of regulation was described in T.

12,13 Because no stool samples could be collected for the control

12,13 Because no stool samples could be collected for the control period, it cannot be determined with certainty that the diarrhea symptoms are caused by the viral pathogens detected in the samples at the symptomatic time point. Indeed, asymptomatic carriage of enteric viruses such as norovirus is frequent during outbreaks.14 Moreover, virus shedding in feces could be prolonged after infection. For norovirus, detection for

up to 2 weeks after the end of symptoms is not rare.15 However, clinical symptoms were consistent with viral infection. One third of patients presented vomiting, which is more frequent in viral gastroenteritis, particularly noroviruses, than in enteroinvasive diarrhea due to bacteria.16,17 Our results confirm the high incidence rate of diarrhea in French forces in N’Djamena as observed Wee1 inhibitor by the epidemiological surveillance. However, the incidence rate was lower than usually observed (588 cases per 1,000 person-years vs 1,428 per 1,000 person-years in 2007). This difference may be due to the study period. Indeed, French forces surveillance data derived from the past 10 years in Chad have shown that there is a drastic increase in diarrhea during the humid season, whereas our study corresponded to the dry season. The seasonal impact on the incidence

rate of TD has already been described in others’ studies.18,19 Seasonal variation is consistent with enteric virus outbreaks, as is usually observed selleckchem in industrialized countries.20 Further studies are needed to determine if there is also a seasonal activity of enteric viruses in Chad. The fact that eating outside the mess (ie, in local restaurants

or in field kitchens) constituted a risk factor for diarrhea may be due to unsafe food handling and serving practices, usually considered at risk for TD.21 Soldiers spending time off-base had the same potential contact with endemic pathogens as any other traveler.22 The protective effect of eating in a temporary encampment is likely related to the predominant use of prepackaged meals in these facilities. The protective effect of prepackaged food is also corroborated by the decreased incidence of diarrhea observed when soldiers were restricted to their quarters and consumed only prepackaged meals in February 2008.3,23 The multivariate analysis underlined the protective ZD1839 cell line effect of always eating at the military mess. This supports the positive effects of the Hazard Analysis and Critical Control Point programs in such structures, which improve food handling and hygiene. In addition, we found subjects to have a fourfold risk of diarrhea if a case of diarrhea was already present in their close circle. As a group effect has been eliminated, this corresponds to a high risk of person-to-person transmission. This is a new insight into TD, and is probably related to the high frequency of enteric viruses identified.

In total, 842 patients who received QFT-GIT or TST and used biolo

In total, 842 patients who received QFT-GIT or TST and used biologic agents

between January 2007 and December 2012 were recruited to determine the usefulness of LTBI screening tests. The incidence of active TB was calculated relative to the LTBI screening method as the number of events per 100 000 person-years exposure. TB occurred in two of the patients who complied with an LTBI prophylaxis strategy. The TB incidence in the group that received both QFT-GIT and TST was 151.05 (95% confidence interval [CI] 150.11–151.98)/100 000 GSI-IX person-years, and the incidence was 169.78 (95% CI 168.73–170.84)/100 000 person-years in the group that received only TST. TB occurred even in some patients who received LTBI prophylaxis in compliance with national guidelines. The incidence of TB in patients who received either the QFT-GIT plus TST

prophylaxis strategy or the TST prophylaxis strategy alone was higher than the annual incidence of the general population of the Republic of Korea. It is not possible to conclude which of the LTBI prophylaxis strategies is superior. “
“Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disorder affecting synovial joints and many other organs. Most patients seen in clinical settings have a progressive chronic disease, with radiographic damage, frequent work disability, incremental functional declines and increased mortality TGF-beta inhibitor rates. The introduction of the biological drugs in treatment of RA has played an important role in prevention of destructive effects of the disease but may have serious adverse effects due to their powerful inhibition of the immune system. To study the adverse effects (ADEs) of three different tumor necrosis factor α inhibitor (TNFi) drugs (infliximab, adalimumab and etanercept) in RA patients for 5 years in the south-west area of Saudi Arabia. Two groups of RA patients were included in this study: The first group included 112

patients, representing the biologics group. These patients received biological therapy plus disease modifying anti-rheumatic drugs (DMARDs): 56 patients received infliximab (IFX), 36 patients received adalimumab (ADL) and 20 patients received etanercept (ETN). The second group also very included 112 patients, representing the control group: RA patients treated only with the traditional DMARDs. ADEs were classified into mild and severe. The mild ADEs which had been recorded during 5 years of follow-up in patients receiving TNFi, were onycholysis (1.8%), positive tuberculin test (1.8%) and small vessel vasculitis (1.8%). Statistically, there were insignificant differences in the mild ADEs except for upper respiratory tract infection that was significantly higher in the control group. Severe ADEs included pneumonia (1.8%) and solid tumor (1.8%) and there were no significant differences between the biologics and control groups.

In addition, overexpression of glycerol-3-phosphate dehydrogenase

In addition, overexpression of glycerol-3-phosphate dehydrogenase (glpD) and glycerol-3-phosphate acyltransferase (plsB) involved in energy metabolism (Spoering et al., 2006) and overexpression of relA involved in ppGpp synthesis (Korch et al., 2003) also caused increased persister BGJ398 ic50 formation. We have recently identified a new persister gene phoU, previously identified as a repressor of phosphate uptake system pstSCAB, in E. coli using a transposon mutagenesis approach (Li & Zhang, 2007). Mutation in PhoU leads to a generalized higher susceptibility than the parent strain to a diverse range of antibiotics and stresses and a defect in persister formation.

Microarray studies indicated that PhoU mutant surprizingly expressed high levels of energy metabolism genes, transporter genes and flagella and chemotaxis genes, which suggests that PhoU is a global repressor for cellular metabolism and its inactivation leads to a hyperactive metabolic state

(Li & Zhang, 2007). We thus proposed a new model of persister formation based on PhoU as a global negative regulator, which suppresses the cellular metabolism of the bacteria by downregulating or shutting down the genes or proteins involved in energy production, membrane transport, SCH772984 price etc., to facilitate persister formation (Li & Zhang, 2007). However, persisters are not homogeneous (Zhang, 2004) and are most likely mediated by multiple mechanisms. To shed further light on possible new persister mechanisms, in this study, taking advantage of our successful experience of screening a transposon mutant library (Li & Zhang, 2007), we screened the E. coli Keio deletion mutant library and identified two new persister genes sucB and ubiF involved in energy metabolism, whose inactivation caused a defect in persister survival as demonstrated by higher susceptibility to different antibiotics and stresses than the parent strain. Ampicillin, norfloxacin, gentamicin, trimethoprim, tetracycline,

kanamycin and chloramphenicol were obtained from Sigma-Aldrich Chemical Co., and their stock solutions were freshly prepared, filter-sterilized and used at appropriate concentrations tuclazepam as indicated. Escherichia coli K-12 parent strain BW25113 and its isogenic deletion mutant library of the Keio collection (Baba et al., 2006) were used for the genetic screens to identify mutants with a defect in persister survival after antibiotic exposure. Escherichia coli cells were routinely grown in Luria–Bertani (LB) medium. For sucB and ubiF mutants, 30 μg mL−1 kanamycin was used, and for complementation of sucB and ubiF mutants, 30 μg mL−1 kanamycin and 30 μg mL−1 chloramphenicol were added. M9 minimal medium with a final concentration of 0.4% glucose and 0.05% magnesium sulfate was used as a nutrient-limiting medium. Saline (0.9% sodium chloride) was used as a condition for the starvation experiment. M9 minimal medium at pH 3.0 and 5.

For this analysis, we also insisted that patients had to be recei

For this analysis, we also insisted that patients had to be receiving an NNRTI-containing regimen at all times between GRTs in a pair, but no restrictions were imposed on the other drugs (Fig. 1 illustrates a virtual patient who was kept on a nevirapine-containing GSK2118436 price regimen). Furthermore, to be sure that patients had experienced failure with resistance, we included only those harbouring a virus predicted by the Rega interpretation system

(IS) to have reduced susceptibility to at least one of the drugs (not necessarily the NNRTI) received at the first GRT; versions 8.0.1 of the Rega IS for the drugs currently in use in clinical practice and 6.4.1 for the remaining drugs (nonboosted PIs, etc.) were used to predict the number of active drugs in the ART regimen at the time of each GRT [15]. Patients’ characteristics at t0 were described and average (mean or median) changes in laboratory markers from t0 to t1 were evaluated using simple regression and multilevel modelling, accounting for nonindependence of observations (with similar results). NNRTI-associated mutations were

those currently listed in the IAS-USA report as of December 2009 [16]. We assumed that NNRTI-associated mutations identified Selleck PD332991 at t0 were still present in a patient’s body at t1, even if they were not actually identified by the GRT at t1. The rate of NNRTI resistance accumulation was calculated as number of NNRTI

mutations detected at t1 that had not been detected at t0 divided by the time between t0 and t1 [and expressed as a rate per person-years of follow-up (PYFU) with a viral load>500 HIV-1 RNA copies/mL while receiving an NNRTI]. A multivariable Poisson regression model was used to identify independent predictors of both NNRTI resistance accumulation and IAS etravirine-specific next mutations. All factors known or thought potentially to be associated with the risk of accumulation of resistance were included in a final multivariable model showing mutually adjusted relative rates (RRs). The full list of predictors included in the multivariable model is shown in Table 3 below. In order to adjust the estimate of the parameters variance to account for the fact that a patient could contribute more than one pair of genotypes, a generalized estimating equation (GEE) model with first-order autoregressive working correlation structures was fitted (but results were robust to the choice of this working matrix) using PROC GENMOD in sas [17,18].

For the above reasons, it is not possible to state how representa

For the above reasons, it is not possible to state how representative the sample used AZD9291 cell line in this analysis is of the population of Scottish travelers dying. Although cause, date, and location of death were available for the analysis,

additional data on traveler type, time the deceased spent abroad before death, and data on risk factor/underlying conditions would have aided in discrimination of possible effectors on death. With respect to the cause of death bias may also have been introduced due to differences in recording the cause of death between different countries including Scotland or even inaccuracy in the cause of death communicated to the SEHD. The data also did not allow the distinction to be made between Scots living abroad (eg, expatriates) and Scots traveling KU-57788 in vitro abroad (eg, on holiday). This may have introduced bias into any comparisons with the reference Scottish population, as factors related to long-term residence abroad may have affected the cause and age at death. In addition, the lack of age-categorized denominator data for Scottish travelers necessitated the assumption that age distribution of UK travelers abroad was representative of Scottish travelers abroad to analyze the relationship between age at death due to circulatory disease and whether death occurred abroad or not. Finally, there are significant limitations related to the comparability of traveling and non-traveling

Scots, where, for example, the Scottish population will include those who for health reasons are unable to travel. In comparing across the age range 25 to 64, it was hoped to eliminate some of this bias associated with underlying conditions and ability to travel associated with older age. A total of 587 bodies were returned to Scotland for cremation between 2000 and 2004. Of these, 177 (30.2%) were females and 408 (69.5%) were males; 2 (0.3%) were not recorded for sex. The mean age at death was 57.8 years (range 0–93 years; median 61 years).

The cause of death was recorded in 572 (97.4%) patients (Table 1). Of these, only 9 (1.5%) were due to infectious causes; one of these was due to cerebral malaria, one due to a viral hemorrhagic fever, and the remainder due to septic shock. Trauma accounted for 120 deaths (20.4%), while other non-infectious causes accounted for 443 (75.5%) deaths. The causes of many of the 120 traumatic deaths were often difficult Niclosamide to accurately ascertain. In most cases (N = 95, 79.2%) they were broadly described as accidental deaths. The remainder consisted of those who died by suicide (17, 14.2%) and conflict (3, 2.5%); the cause was unrecorded in 5 (4.2%). Among those deaths which were neither caused by trauma nor infection (Table 2), the major cause of death was failure of the circulatory system (341, 77.0%) which contributed to 52.0% of all deaths. This was followed by failure of the respiratory (41, 9.3%) and gastrointestinal (20, 4.5%) systems with neoplasm accounting for 18 deaths (4.1%).

UniFrac distances ranged from 0298 to 0607 and were higher betw

UniFrac distances ranged from 0.298 to 0.607 and were higher between the initial and late stage samples. UniFrac tests have been previously used as a semi-quantitative determination of the similarities between the bacterial communities on the phyllosphere of Populus deltoides sampled at different times (Redford et al., 2010). According to our estimations, major changes

in the phenol-degrading bacterial community may occur between the initial and midterm stages of leaf decomposition. At the midterm, the greatest community richness and diversity was found and coincided with increasing phenol Galunisertib concentration oxidase activity and maximum fungal biomass (Artigas et al., 2011). The LmPH sequences from this stage were scattered throughout the phylogenetic tree (in clusters A, B, C, and E), and their corresponding enzymes exhibit different kinetic properties. selleck monoclonal humanized antibody inhibitor It is known that bacteria and fungi have complementary roles in leaf litter degradation. Bacteria are thought to increase their contribution only after leaf material has been partially broken down (Baldy et al., 1995), whereas fungi, especially

aquatic hyphomycetes, have been recognized as dominant, in terms of both activity and biomass, during early decomposition (Gulis & Suberkropp, 2003; Romaní et al., 2006). However, bacteria may make a greater contribution to leaf litter decomposition particularly when fungal activity is compromised by unfavorable conditions (Pascoal & Cassio, 2004; Kubartova et al., 2009). In conclusion, by analyzing the LmPH gene from different leaf decomposition stages, we have shown that the bacterial community changes significantly over the course of leaf litter degradation in streams. During Bcl-w early decomposition, the bacterial community is rather complex and potentially exhibits a low degree of metabolic

specialization in view of the deduced enzyme kinetics. As decomposition progresses, the phenol-degrading bacterial community is dominated by suspected low-Ks type bacteria, with a high similarity to Alcaligenes spp., Comamonas sp., and Ralstonia sp, suggesting a gradual selection of specialized phenol degraders as decomposition progressed. To the best of our knowledge, this work represents the first specific analysis of any functional gene marker and of bacterial and fungal origin, used for investigating microbial communities during the leaf litter decomposition process in streams. Time series analyses of bacterial and fungal communities in leaf litter decomposition have previously been performed using either DGGE or terminal-restriction fragment length polymorphism (T-RFLP) of amplified SSU rRNA fragments (Das et al., 2007; Marks et al., 2009; Kelly et al., 2010), although no general conclusions can be derived from these studies. The relative presence of general and specialized microorganisms on leaf surfaces during litter decomposition has been proposed as a major determinant of diversity (Das et al., 2007).

UniFrac distances ranged from 0298 to 0607 and were higher betw

UniFrac distances ranged from 0.298 to 0.607 and were higher between the initial and late stage samples. UniFrac tests have been previously used as a semi-quantitative determination of the similarities between the bacterial communities on the phyllosphere of Populus deltoides sampled at different times (Redford et al., 2010). According to our estimations, major changes

in the phenol-degrading bacterial community may occur between the initial and midterm stages of leaf decomposition. At the midterm, the greatest community richness and diversity was found and coincided with increasing phenol Talazoparib oxidase activity and maximum fungal biomass (Artigas et al., 2011). The LmPH sequences from this stage were scattered throughout the phylogenetic tree (in clusters A, B, C, and E), and their corresponding enzymes exhibit different kinetic properties. learn more It is known that bacteria and fungi have complementary roles in leaf litter degradation. Bacteria are thought to increase their contribution only after leaf material has been partially broken down (Baldy et al., 1995), whereas fungi, especially

aquatic hyphomycetes, have been recognized as dominant, in terms of both activity and biomass, during early decomposition (Gulis & Suberkropp, 2003; Romaní et al., 2006). However, bacteria may make a greater contribution to leaf litter decomposition particularly when fungal activity is compromised by unfavorable conditions (Pascoal & Cassio, 2004; Kubartova et al., 2009). In conclusion, by analyzing the LmPH gene from different leaf decomposition stages, we have shown that the bacterial community changes significantly over the course of leaf litter degradation in streams. During Alanine-glyoxylate transaminase early decomposition, the bacterial community is rather complex and potentially exhibits a low degree of metabolic

specialization in view of the deduced enzyme kinetics. As decomposition progresses, the phenol-degrading bacterial community is dominated by suspected low-Ks type bacteria, with a high similarity to Alcaligenes spp., Comamonas sp., and Ralstonia sp, suggesting a gradual selection of specialized phenol degraders as decomposition progressed. To the best of our knowledge, this work represents the first specific analysis of any functional gene marker and of bacterial and fungal origin, used for investigating microbial communities during the leaf litter decomposition process in streams. Time series analyses of bacterial and fungal communities in leaf litter decomposition have previously been performed using either DGGE or terminal-restriction fragment length polymorphism (T-RFLP) of amplified SSU rRNA fragments (Das et al., 2007; Marks et al., 2009; Kelly et al., 2010), although no general conclusions can be derived from these studies. The relative presence of general and specialized microorganisms on leaf surfaces during litter decomposition has been proposed as a major determinant of diversity (Das et al., 2007).