vaginosis and Prevotella bivia (Aroutcheva et al, 2001a) Consis

vaginosis and Prevotella bivia (Aroutcheva et al., 2001a). Consistent with this, Lactobacillus strains have been isolated from the human vaginal microbiota for probiotic use against vaginosis-associated pathogens (Reid & Burton, 2002; Reid et al., 2003) on the basis of their ability to produce high levels of hydrogen peroxide (Klebanoff et al., 1991; Hillier et al., 1992, 1993). Moreover, Pridmore et al. (2008) first reported for an

intestinal Lactobacillus that hydrogen peroxide contributes to the killing activity NVP-BGJ398 order of L. johnsonii NCC533 against serovar Typhimurium. Consistent with these reports, here, we observed that hydrogen peroxide concentration-dependently kills serovar Typhimurium, G. vaginosis and UPEC strains. Moreover, we report that lactic acid acts synergistically with hydrogen peroxide to kill G. vaginalis, S. typhimurium and UPEC more efficiently. The mechanism underlying the stimulatory effect of lactic acid observed could be related to the observation by Greenacre et al. (2006), who have reported that the lactic acid-induced acid tolerance response causes hydrogen peroxide sensitivity in serovar Typhimurium via the downregulation

of the OxyR regulon. A second mechanism could also be proposed, find more resulting from the permeabilizing effect of lactic acid on the gram-negative bacterial outer membrane (Alakomi et al., 2000), thus facilitating the passage of molecules across the membrane, and in turn increasing the killing effects of antimicrobial compounds (Niku-Paavola et al., 1999; Alakomi et al., 2000). “
“Candidatus Methylomirabilis oxyfera’; is a polygon-shaped bacterium Branched chain aminotransferase that was shown to have the unique ability to couple anaerobic methane oxidation to denitrification, through a newly discovered intra-aerobic pathway. Recently, the complete genome of Methylomirabilis oxyfera was assembled into a 2.7-Mb circular single chromosome by metagenomic sequencing. The genome of M. oxyfera

revealed the full potential to perform both methane oxidation and the conversion of nitrite via nitric oxide into oxygen and dinitrogen gas. In this study, we show by immunogold localization that key enzymes from both methane- and nitrite-converting pathways are indeed present in single M. oxyfera cells. Antisera targeting the particulate methane monooxygenase (pMMO) and the cd1 nitrite reductase (NirS) were raised and used for immunogold localization in both single- and double-labelling experiments. Our previous studies have shown that M. oxyfera does not develop pMMO-containing intracytoplasmic membranes as is observed in classical proteobacterial methanotrophs. Our results suggest that in M. oxyfera, the pMMO and NirS enzymes localized to the cytoplasmic membrane and periplasm, respectively. Further, double-labelling showed co-occurrence of pMMO and NirS in single M. oxyfera cells.

, 2000) To date, a number of SEs have been identified, including

, 2000). To date, a number of SEs have been identified, including SEA-E, SEG, SEH, SEI, SEJ, SEK, SEL, SEM, SEN, and SEO (Omoe et al., 2002). Although their exact mechanisms of action have not been fully elucidated, these enterotoxins are believed to stimulate an enteric-vagus nerve reflex, triggering the vomiting centres of the brain (Sears & Kaper, 1996). Licochalcone A is one of the many flavonoids present in Chinese liquorice root, which has been used for centuries in traditional Chinese medicine. It has been demonstrated that licochalcone A possesses a variety of biological activities, including antimicrobial (Fukai et al., 2002), selleck chemical anti-inflammatory (Kwon et

al., 2008), antiprotozoal (Chen et al., 2001), antitumour (Shibata, 2000), and antioxidative (Haraguchi et al., 1998) activities. Strikingly, previous studies have shown that licochalcone A was potent against methicillin-sensitive S. aureus BIBW2992 (MSSA) and methicillin-resistant S. aureus (MRSA), with minimum inhibitory concentrations (MICs) ranging from 3 to 16 μg mL−1 depending on the strain (Hatano et al., 2000; Fukai et al., 2002). These results indicate that licochalcone A could be a potentially effective antimicrobial against S. aureus and could be used to treat patients infected with drug-resistant bacteria. Furthermore, in our previous study, we reported that subinhibitory concentrations of licochalcone A significantly

decreased α-toxin production in both MSSA and MRSA isolates (Qiu et al., 2009). However, there were no data on enterotoxin secretion by S. aureus exposed to licochalcone A obtained in this study. The present study Protein kinase N1 was aimed to investigate the influence of subinhibitory concentrations of licochalcone A on

the production of enterotoxins A and B by S. aureus. The clinical isolate MRSA 2985 was isolated at the First Hospital of Jilin University from a blood sample from an infected patient. The MSSA ATCC 29213 isolate was obtained from the American Type Culture Collection (ATCC). Licochalcone A was purchased from the National Institute for the Control of Pharmaceutical and Biological Products (Beijing, China), and stock solutions at various concentrations were prepared in dimethyl sulphoxide (DMSO) (Sigma-Aldrich, St. Louis, MO). The MIC in Mueller–Hinton broth (BD Biosciences Inc., Sparks, MD) was evaluated in triplicate using a broth microdilution method as recommended by the Clinical and Laboratory Standards Institute (2005). The licochalcone A MIC values for S. aureus strain ATCC 29213 and MRSA strain 2985 were 4 μg mL−1. Furthermore, the MICs of the strains vs. licochalcone A in Luria-Bertani (LB) broth (BD Biosciences Inc.) were also 4 μg mL−1. Staphylococcus aureus strain ATCC 29213 was grown to an OD600 nm value of 0.3 in LB, and 100-mL volumes of the culture were placed into five 250-mL Erlenmeyer flasks.

These effects after 6 h could be partially correlated with the no

These effects after 6 h could be partially correlated with the nonmotile phenotype of the ompR mutant, because a similar biofilm structure was observed with the nonmotile flhDC mutant. Furthermore, the reduction in the biofilm formation capacity of the ompR strain after 24 h might be correlated with the low adhesion abilities of this mutant. Reduced

adherence could be responsible for the less efficient attachment of cells and the loose structure of the biofilm. These results also suggest that the loss of YompC from the outer membrane of the ompR mutant contributed to the reduced biofilm formation by this strain. The regulation of motility and biofilm development by OmpR in strain Ye9 (serotype O9, biotype 2) seems to be different from that in Y. enterocolitica JB580v (serotype O8 biovar 1B). Kim et al. (2008) demonstrated the importance of OmpR in the motility of JB580v, but the ompR mutant of this strain, unlike that of Ye9, showed no impairment in flagella production. In addition, contrary to our findings, the OmpR of JB580v appeared not to perform a regulatory function in biofilm initiation and production. The Y. enterocolitica species BYL719 mouse is quite heterogeneous with six distinct biovars (1A, 1B, 2, 3, 4 and 5) distinguished according to their pathogenicity, geographic distribution and ecological

niche (Bottone, 1999). It has been shown that the highly pathogenic strain 8081 of Y. enterocolitica biovar 1B contains an assortment see more of genes not present in the biovar 2 and vice versa (Thomson et al., 2006). The results of the present study and those of Kim et al. (2008) suggest that genetic variation in separate

biovars of Y. enterocolitica may lead to different flagella and biofilm production phenotypes. In addition, this study shows that merely recording the many phenotypic changes caused by mutation of OmpR is insufficient to discern which of the functions of this regulator are responsible for certain behaviors of Y. enterocolitica cells that confer an advantage in a particular ecological niche. This work was supported by Warsaw University (grant BW 2007) and by the Polish Ministry of Science and Higher Education (grant N303 009 32/0537). “
“Kochi Core Center, Japan Agency for Marine – Earth Science and Technology (JAMSTEC), Nankoku, Kochi, Japan A total of 71 isolates were collected from lake sediment and soil surrounding lakes in the Skarvsnes area, Antarctica. Based on ITS region sequence similarity, these isolates were classified to 10 genera. Twenty-three isolates were categorized as ascomycetous fungi from five genera (Embellisia, Phoma, Geomyces, Tetracladium or Thelebolus) and 48 isolates were categorized as basidiomycetous fungi in five genera (Mrakia, Cryptococcus, Dioszegia, Rhodotorula or Leucosporidium). Thirty-five percent of culturable fungi were of the genus Mrakia. Eighteen isolates from eight genera were selected and tested for both antifreeze activity and capacity for growth under temperatures ranging from −1 to 25 °C.

2e) It has been demonstrated previously that invasin plays a maj

2e). It has been demonstrated previously that invasin plays a major role in the early invasion of PPs by yersiniae in the mouse infection model (Pepe & Miller, 1993; Pepe et al., 1995; Marra & Isberg, 1996, 1997). PPs were, however, shown to be eventually colonized by yersiniae at later infection stages (Pepe & Miller, 1993). The spread of yersiniae to the spleen and liver as well as LD50 were not dependent on inv. The effect of invasin on the Selleck CYC202 colonization of individual PPs has, however, not been studied. We therefore quantified the colonization of individual PPs using luminescing yersiniae on day 5 p.i. Fourteen mice

were infected with either the Δinv mutant or the wild-type strain. Analysis of PPs with the IVIS camera revealed significantly fewer luminescing PPs after oral infection with the Δinv mutant than wild-type

yersiniae (Fig. 3a). In fact, most PPs did not show any luminescence at all. This was also the case for mice infected for 6 or 7 days (results not shown). Therefore, these experiments show that the inv deletion does selleckchem not lead to a delayed invasion phenotype, but rather to invasion and abscessing of fewer PPs. Similarly, the number of abscessed follicles in the cecum (Fig. 3b) as well as the number of mice with abscessed cervical and mesenteric lymph nodes (Fig. 3c and d) were significantly reduced. The spleens and livers of mice infected with the Δinv mutant were, however, more heavily colonized than spleens and livers infected with wild-type yersiniae (Fig. 4). Although this effect was not statistically significant, it was very reproducible in multiple experiments. Interestingly, it was discovered recently that the presence of invasin in Yersinia pseudotuberculosis inhibited colonization of the liver and spleen after intravenous infection (Hudson & Bouton, 2006). In conclusion, these experiments demonstrate Sitaxentan the versatility

of the luxCDABE reporter for analyzing and quantifying Yersinia abscessed tissue in mice. Using this method, we could show for the first time that cervical lymph nodes are frequently abscessed by yersiniae and that the absence of inv leads to a reduced number (rather than delayed invasion) of abscessed PPs, cecal lymph follicles, and cervical lymph nodes. Holger Loessner is acknowledged for plasmids pHL289 and pUX-BF13. This work was supported by DFG grant TR 740/2-1. “
“A rapid, high-resolution melting (HRM) analysis protocol was developed to detect sequence variations associated with resistance to the QoIs, benzimidazoles and dicarboximides in Botrytis cinerea airborne inoculum. HRM analysis was applied directly in fungal DNA collected from air samplers with selective medium. Three and five different genotypes were detected and classified according to their melting profiles in BenA and bos1 genes associated with resistance to benzimidazoles and dicarboximides, respectively.

, 2005) Other plasmids frequently used in BF638R are also diffic

, 2005). Other plasmids frequently used in BF638R are also difficult or impossible to introduce into BF 9343 (data not shown). In general, more efficient transposon mutagenesis is achieved by prior modification of plasmid carrying the transposon by the host of interest. We developed an improved system for transposon mutagenesis in BF using the EZ::TN5 system. Previous attempts to mutagenize BF by transposons have been hindered

by either vector integration and/or multiple insertions (Shoemaker et al., 1986; Chen et al., 2000a). Also, those methods often used labor-intensive filter mating techniques to introduce the DNA. The method described here has several advantages: (1) transposons can be introduced into BF by electroporation, (2) all insertion events are independent, (3) no vector delivery

Selumetinib clinical trial system is required and vector cointegration can be completely avoided, and (4) no suicide vector or native inducible promoters to drive transposase expression are needed. We found that the transposon inserts evenly across the chromosome. Also, analysis of the insertion points of the EZ::TN5 transposon indicates that although there is some sequence context preferred of insertion by Tn5, the insertion is sufficiently random for its effective use in construction a library of transposon mutants (Shevchenko et al., 2002). EZ::TN5 transposon mutagenesis also provides flexibility for subsequent identification of the transposon-disrupted gene. For example, if the genome sequence is not available IDH phosphorylation for Nitroxoline the organism of interest, the genes adjacent to the mutated gene can be retrieved and identified by rescue cloning and sequencing. On the other hand, if the genome sequence is available, the mutated gene can be amplified by SRP-PCR and identified by genomic means and large numbers of mutants can be easily screened. Prior passage of the transposon vector in related strains increases downstream efficiency of transposon mutagenesis. This system provides a useful genetic tool that will facilitate deeper understanding of

the pathogenic mechanisms of this important human commensal/pathogen. This research is based upon work supported in part by the Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Biomedical Laboratory Research and Development and in part by the NIAID (NIH) Grant Number 1R56AI083649-01A2. We would like to thank Drs Elizabeth Tenorio and Yi Wen for their helpful comments and advice regarding mutant identification and Southern Blots, respectively. “
“Rapid detection of yeast contamination is important in the food industry. We have developed loop-mediated isothermal amplification (LAMP) assays to detect the emerging opportunistic pathogenic yeasts: Candida albicans, Candida glabrata, Candida tropicalis, the Candida parapsilosis group, Trichosporon asahii, and Trichosporon mucoides.

Both descriptions of side-effects and their impact on daily activ

Both descriptions of side-effects and their impact on daily activities, personal life and Everolimus supplier socialisation

were documented [15.4%, n = 65]. Of the 61 [14.5%] comments around efficacy, most indicated perceived dependence on medicines for symptom relief, performance of daily activities, and prolonging life, although some perceived inadequate efficacy. There were 59 [14%] comments articulating respondents’ general attitudes towards medicines, including worries about adherence, dependence, interactions, and generics. Relationships with healthcare providers were mentioned in 58 [13.8%] comments, many suggesting that medicines-related discussions were inadequate, failing to consider individuals’ concerns. Some respondents lacked trust and confidence in providers, and desired comprehensive, updated and meaningful

information about medicine risks and benefits; nineteen [4.5%] described searching for additional information. A few respondents described having little control over medicine regimes and brands [1.7%, n = 7]. This study revealed a wide range of medicine-related experiences among the general public, and their impact on day-to-day lives. The population in this study was entirely self-selected and, given the on-line promotional methods used, potentially attractive to those with issues they wanted to raise through self-help forums. However, the findings are comparable to other, qualitative studies1 which suggest that many people have negative experiences of using regular medicines. Health care professionals

need to recognise the magnitude of medicine-induced burden which some individuals see more experience. While a method of identifying those with the greatest medication-burden could be valuable in helping to optimise medicines use, our results suggest that a simple open question may encourage individuals out to raise key issues of concern to them. 1. Pound P et al. Resisting medicines: a synthesis of qualitative studies of medicine taking. Soc Sci Med. 2005; 61:133–155. 2. Krska J, Morecroft CW, Rowe PH, Poole H. A novel instrument to measure medicines-related quality of life [Abstract]. Int J Clin Pharm. 2013; 35:488. S. Karima,b, S. Hussaina, K. Hodsonb, R. Hornec aHeathwerwood and Wexham Park NHS Foundation Trusts, Slough, UK, bCardiff University, Cardiff, UK, cUCL School of Pharmacy, London, UK Counselling patient prior to discharge has a major impact on their use of medicines. Cardiology patients counselled by a pharmacist were more satisfied with the information received about their medicines. Patients at high risk should be prioritised to receive counselling by a pharmacist. The Royal Pharmaceutical Society (RPS) released guidance ‘Keeping patients safe when they transfer between care providers – getting the medicines right’, which aimed to bridge the gap between different care sectors.

No such signal was found in the MERIT study for treatment-naïve p

No such signal was found in the MERIT study for treatment-naïve patients. MVC has also been associated with postural hypotension Selleck CDK inhibitor when used at

higher than recommended doses in healthy volunteers; patients with a history of postural hypotension, renal impairment or taking antihypertensive agents may be at increased risk [209]. In view of the limited data available, special caution should be exercised in the use of MVC in patients with a high CVD risk and use of alternative agents, where possible, considered. The following guidance considers issues concerning the initiation and choice of ART for HIV-positive women who are not currently pregnant. For guidance on the management of pregnancy in HIV-positive woman please refer to the BHIVA guidelines for the management of HIV infection in pregnant women 2012 [210]. There are few specific data on ART treatment in women other than in pregnancy. Data available are largely from a meta-analysis, post hoc analyses or derived from cohort studies. The majority of the randomized clinical trial data on ART comes from studies that have enrolled mostly male subjects. If RCTs do enrol women, the numbers are often too small to draw significant gender-based

conclusions. Approximately one-third of people diagnosed with, and accessing care, for HIV in the UK are women [211]. The majority are of childbearing age but the age range is increasing, adding the complexity of menopause and its sequelae to the management of HIV-positive women.

Many HIV-positive women in the UK are of African heritage and face overlapping challenges to their health and well-being [212]. Women’s experience of HIV reflects multiple social and cultural influences, which when combined Lepirudin with sex-specific biological factors influence individual responses to HIV. We recommend therapy-naïve HIV-positive women who are not pregnant start ART according to the same indicators as in men (see Section 4: When to start) 1A. Proportion of HIV-positive women with CD4 cell count <350 cells/μL not on ART. Gender differences in HIV VL and CD4 cell count at different stages of infection have been observed [213] but have not been consistently associated with long-term clinical outcomes for HIV-positive women. Based on current data, the indications for starting ART do not differ between women who are not pregnant and men. Gender-specific socio-economic and cultural factors may impact on women’s ability to access care and manage their medication, compromising their ability to initiate and adhere to therapy, and they may require support from the multidisciplinary team. We recommend therapy-naïve HIV-positive women start ART containing two NRTIs and one of the following: PI/r, NNRTI or INI (1A), as per therapy-naïve HIV-positive men.

Membranes were prepared from E coli murG(Ts);pAZI8952 grown at 4

Membranes were prepared from E. coli murG(Ts);pAZI8952 grown at 42 °C in 0.2% arabinose to assay Mtu MurG. Unfortunately, Dapagliflozin clinical trial no MurG activity was detected in these membranes (see data below and Table 2). Activity was undetectable even in the membranes of transformants grown in 2% arabinose to obtain higher levels of Mtu MurG. The lack of MurG activity was surprising given that the Mtu murG complemented the E. coli (Ts) homologue and must have been functional. Activity was checked in the peptidoglycan synthesis assay in case the specific activity of the Mtu MurG protein was very low, because this assay is more sensitive than the MurG

assay (Chandrakala et al., 2001; Ravishankar et al., 2005). No cross-linked peptidoglycan synthesis was detected in these membranes (Table 2), whereas the expected level of activity was observed in the membranes of wild-type E. coli grown at 37 °C. The assay time, temperature and quantity

of protein were varied in an attempt to improve the sensitivity but peptidoglycan synthesis remained undetectable. Both MurG and peptidoglycan synthesis assays are dependent on having a functional MraY (Fig. 1a). However, the MraY enzyme was active in the membranes of the transformant, and the activity was similar to that in membranes from wild-type E. coli (strain AMA1004) grown at 37 °C (Table 1). This indicated that the block in peptidoglycan synthesis was downstream of the MraY and was probably due to the

lack of MurG activity in these membranes. Either the learn more Mtu MurG protein was unstable under Idoxuridine the conditions of membrane preparation and storage, or the specific activity of the Mtu MurG protein was below the limit of detection or the assay conditions were not appropriate for Mtu MurG. It is not obvious how membranes devoid of MurG can be made under normal circumstances, as murG is an essential enzyme. This result, while unexpected, offered an opportunity. Because the membranes contained the lipid carrier and all enzymes involved in peptidoglycan synthesis other than MurG, they provided a powerful assay system for MurG, provided that the addition of the pure enzyme could reconstitute the system. For ease of description, these membranes are referred to as E. coli(Ts) ΔMurG membranes. Membranes from wild-type E. coli or the Ts mutant cannot be used to assay exogenous MurG because the endogenous MurG activity would mask the activity. Solubilized, purified E. coli MurG (2 μg) was added to the membranes of E. coli(Ts) ΔMurG incubated with the two UDP-linked sugar precursors under conditions for peptidoglycan synthesis. Considerable cross-linked peptidoglycan was synthesized (Table 2). This indicates that the exogenous E. coli MurG protein was not only able to access the lipid carrier in the membrane, but also able to interact with other membrane and enzyme components to reconstitute peptidoglycan synthesis in these membranes.

2) Starmerella bombicola NRRL Y-17069 produced a major di-O-acet

2). Starmerella bombicola NRRL Y-17069 produced a major di-O-acetylated lactone form of sophorolipid ([M+Na]+, m/z 711), plus a minor component of this as the free acid form ([M+Na]+, m/z 729). This latter ion is complicated by an adjacent ion at m/z 727 that is assigned as the potassium adduct ([M+K]+) of the major lactone form. By contrast, C. stellata, Candida sp. NRRL Y-27208 and C. riodocensis produced very little of this lactone form (Fig. 2), and the major ion (m/z 729) for these three species is attributed to a di-O-acetyl free acid form. These strains also produced free acid forms of the monoacetylated

and non-acetylated sophorolipids characterized by MALDI-TOF MS ions at m/z 687 and m/z 645. Candida find more riodocensis and Candida sp. NRRL Y-27208, but not C. stellata, also produced monoacetylated sophorolipid in the lactone form ([M+Na]+, m/z 669). The greatest heterogeneity for sophorolipid production was observed for C. apicola NRRL Y-2481. Similar to S. bombicola, this strain mainly produced lactone

sophorolipids, although with C. apicola, the di-O-acetyl (m/z 711), mono-O-acetyl (m/z 669) and non-acetyl (m/z 627) forms were observed. The free acid forms of these three sophorolipids were also observed as minor components from C. apicola, as characterized by ions 18 Da larger at m/z 729, m/z 687 and m/z 645, respectively (Fig. 2). Interestingly, the free acid form was the major component of sophorolipids produced by C. batistae (Konoshi et al., 2008). Epigenetics inhibitor This study demonstrated that in addition to S. bombicola, C. apicola and C. batistae, three other species of the Starmerella clade synthesize significant amounts of sophorolipids, i.e., C. riodocensis, C. stellata and Candida sp. NRRL Y-27208. Based on our phylogenetic analysis, sophorolipids were produced only by members of the S. bombicola subclade of the Starmerella clade. MALDI-TOF MS showed certain of the species to produce sophorolipids predominantly

in the lactone form, whereas the other species predominantly gave the free acid form. It should be noted that although MALDI-MS is well PAK5 suited for the rapid screening and characterization of sophorolipids with diverse molecular mass, it is unable to distinguish between positional isomers, such as differences in the location of acetyl groups, or the fatty acid double bond or acyl-glycosidic linkage. For this reason, a more complete structural characterization of the sophorolipids from Candida sp. NRRL Y-27208 will be published later. We thank Eleanor Basehoar-Powers and Trina Hartman for technical assistance and Jamie Schroderus for graphics assistance in preparation of Fig. 1. The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned.

Magnetotactic bacteria (MTB) are ubiquitous in aquatic environmen

Magnetotactic bacteria (MTB) are ubiquitous in aquatic environments, for example marines and lakes. They can form intracellular nanosized magnetite or greigite crystals, known as magnetosomes, which are membrane bound and are generally organized into one or more chains (Schüler, 2008). The net magnetic moment of magnetosome chains can interact with the Earth’s magnetic field and thus navigate MTB along local geomagnetic fields (magnetotaxis) (Faivre & Schüler, 2008). It is widely believed that the magnetotaxis

in conjunction with aerotaxis and other chemotaxis can help MTB to efficiently locate and maintain the most optimal position in vertically stratified sediments or water columns (Frankel et al., 1997; Pan et al., 2009b). All currently known MTB belong to the Proteobacteria and Nitrospira phyla based on the comparison of 16S rRNA genes (Amann et al., 2006). MTB can play important roles in mediating some geochemical SCH772984 mouse processes, for example iron and sulfur cycling (Simmons & Edwards, 2006). Moreover, fossil magnetosomes preserved in sediments are important natural remanent magnetization carriers (Chang Avasimibe price & Kirschvink, 1989; Moskowitz et al., 1993; Pan et al., 2005a, b; Kopp & Kirschvink, 2008), and can serve as a potential proxy for paleoenvironmental reconstruction

(Snowball et al., 1999; Snowball et al., 2002; Paasche et al., 2004; Kopp & Kirschvink, 2008). Therefore, understanding the patterns of MTB communities in environments is of great importance. A handful of studies have examined the

diversity and vertical distribution of MTB in a single location and have shown that the majority of MTB are usually close to the oxic–anoxic transition zone in chemically Tobramycin stratified aquatic habitats (Spring et al., 1992, 1993; Bazylinski et al., 1995; Bazylinski & Frankel, 2004; Simmons et al., 2004; Flies et al., 2005a; Pan et al., 2008; Lin & Pan, 2009; Lin et al., 2009). However, due to the lack of detailed studies, the distribution of MTB communities between different locations and their temporal variations remain unclear (Spring et al., 1994; Flies et al., 2005b). Our previous studies revealed that large amounts of MTB (up to 106 cells mL−1) existed in sediments from Lake Miyun near Beijing, China, where the enriched MTB affiliated within both Proteobacteria and Nitrospira phyla (Lin et al., 2008, 2009). In the present study, we used a combination of a cultivation-independent approach and unifrac analysis to investigate the temporal variations of MTB in two freshwater sediment microcosms, which were collected from two separate sites in Lake Miyun, Beijing. The diversity and variation of MTB communities in two microcosms were also compared. The MTB-bearing sediment samples used in this study were collected from two separate sites (MY8 and MY11) in the southern margin of Lake Miyun near Beijing, China (Fig. 1).