Role of humic substances in promoting autotrophic growth in nitrate-dependent iron-oxidizing bacteria.

Nitrate-dependent iron oxidation was discovered in 1996 and has been reported from various environments ever since. To date, despite the widespread nature of this process, all attempts to cultivate chemolithoautotrophic nitrate-dependent iron oxidizers have been unsuccessful. The present study was focused on understanding the influence of natural chelating agents of iron, like humic substances, on the culturability, activity, and enumeration, of these microorganisms. Pure culture studies conducted with Thiobacillus denitrificans showed a constant increase in cell mass with a corresponding nitrate-dependent iron oxidation activity only when Fe(II) was provided together with humic substances, compared to no growth in control incubations without humic substances. The presence of a relatively strong chelating agent, such as EDTA, inhibited the growth of Thiobacillus denitrificans. It was concluded that complex formation between humic substances and iron was required for chemolithoautotrophic nitrate-dependent iron oxidation. Most probable number enumerations showed that numbers of chemolithoautotrophic nitrate-dependent iron-oxidizing bacteria were one to three orders of magnitude higher in the presence of humic substances compared to media without. Similar results were obtained when potential nitrate-dependent iron oxidation activity was determined in soil samples. In summary, this study showed that humic substances significantly enhanced the growth and activity of autotrophic nitrate-dependent iron-oxidizing microorganisms, probably by chelation of iron

Methane emission from feather moss stands.

Data from remote sensing and Eddy towers indicate that forests are not always net sinks for atmospheric CH4. However, studies describing specific sources within forests and functional analysis of microorganisms on sites with CH4 turnover are scarce. Feather moss stands were considered to be net sinks for carbon dioxide, but received little attention to their role in CH4 cycling. Therefore, we investigated methanogenic rates and pathways together with the methanogenic microbial community composition in feather moss stands from temperate and boreal forests. Potential rates of CH4 emission from intact moss stands (n = 60) under aerobic conditions ranged between 19 and 133 pmol CH4 h-1 gdw-1. Temperature and water content positively influenced CH4 emission. Methanogenic potentials determined under N2 atmosphere in darkness ranged between 22 and 157 pmol CH4 h-1 gdw-1. Methane production was strongly inhibited by bromoethane sulfonate or chloroform, showing that CH4 was of microbial origin. The moss samples tested contained fluorescent microbial cells and between 104 and 105 copies per gram dry weight moss of the mcrA gene coding for a subunit of the methyl CoM reductase. Archaeal 16S rRNA and mcrA gene sequences in the moss stands were characteristic for the archaeal families Methanobacteriaceae and Methanosarcinaceae. The potential methanogenic rates were similar in incubations with and without methyl fluoride, indicating that the CH4 was produced by the hydrogenotrophic rather than aceticlastic pathway. Consistently, the CH4 produced was depleted in 13C in comparison with the moss biomass carbon and acetate accumulated to rather high concentrations (3-62 mM). The δ13C of acetate was similar to that of the moss biomass, indicating acetate production by fermentation. Our study showed that the feather moss stands contained active methanogenic microbial communities producing CH4 by hydrogenotrophic methanogenesis and causing net emission of CH4 under ambient conditions, albeit at low rates

Tracing long-distance electron transfer and cable bacteria in freshwater sediments by agar pillar gradient columns.

Cable bacteria (CB) perform electrogenic sulphur oxidation (e-SOX) by spatially separating redox-half-reactions over cm-distances. For freshwater systems, the ecology of CB is not yet well understood, partly because they proved difficult to cultivate. This study introduces a new "agar pillar" approach to selectively enrich and investigate CB-populations. Within sediment columns, a central agar pillar is embedded, providing a sediment-free gradient-system in equilibrium with the surrounding sediment. We incubated freshwater sediments from a streambed, a sulfidic lake, and a hydrocarbon polluted aquifer in such agar pillar columns. Microprofiling revealed typical patterns of e-SOx, such as the development of a suboxic zone and the establishment of electric potentials. The bacterial communities in the sediments and agar pillars were analysed over depth by PacBio near-full-length 16S rRNA gene amplicon sequencing, allowing for a precise phylogenetic placement of taxa detected. The selective niche of the agar pillar was preferentially colonized by CB related to Candidatus Electronema for surface-water sediments, including several potentially novel species, but not for putative groundwater CB affiliated with Desulfurivibrio spp. The presence of CB was seemingly linked to co-enriched fermenters, hinting at a possible role of e-SOx-populations as an electron sink for heterotrophic microbes. These findings add to our current understanding of the diversity and ecology of CB in freshwater systems, and to a discrimination of CB from surface and groundwater sediments. The agar pillar approach provides a new strategy that may facilitate the cultivation of redox gradient-dependent microorganisms, including previously unrecognized CB populations

Assessing Usefulness of High-Resolution Satellite Imagery (HRSI) for Re-Survey of Cadastral Maps

The Government of India has initiated “National Land Records Modernization Programme (NLRMP)” with emphasis to modernize management of land records, minimize scope of land/property disputes, enhance transparency in the land records maintenance system, and facilitate moving eventually towards guaranteed conclusive titles to immovable properties in the country. One of the major components of the programme is survey/re-survey and updating of all survey and settlement records including creation of original cadastral records wherever necessary. The use of ETS/GPS, Aerial or High Resolution Satellite Images (HRSI) and hybrid method of images are suggested for re-survey in the guidelines. The emerging new satellite technologies enabling earth observation at a spatial resolution of 1.0m or 0.5m or even 0.41m have brought revolutionary changes in the field of cadastral survey. The highresolution satellite imagery (HRSI) is showing its usefulness for cadastral surveys in terms of clear identification of parcel boundaries and other cultural features due to which traditional cadastre and land registration systems have been undergoing major changes worldwide. In the present research study, cadastral maps are derived from ETS/GPS, HRSI of 1.0m and 0.5m and used for comparison. The differences in areas, perimeter and position of parcels derived from HRSI are compared vis-a-vis ETS/GPS boundaries. An assessment has been made on the usefulness of HRSI for re-survey of cadastral maps vis-a-vis conventional ground survey

Five‐year histological and serological follow‐up of operationally tolerant pediatric liver transplant recipients enrolled in WISP‐R

Pediatric liver transplant recipients arguably have the most to gain and the most to lose from discontinuing immunosuppression (IS). While IS undoubtedly exerts a cumulative toll, there is concern that insufficient or no IS may contribute to allograft deterioration. Twelve pediatric recipients of parental living donor liver grafts, identified as operationally tolerant through complete IS withdrawal (WISP-R; NCT00320606) were followed for a total of five years (one year of IS withdrawal and four years off IS) with serial liver tests, auto- and allo-antibody assessments. Liver biopsies were performed two and four years off IS and, at these time points, immunoglobulin G (IgG) subclass and C1q binding activity for donor specific antibodies (DSAs) were determined. There were no cases of chronic rejection, graft loss, or death. Allografts did not exhibit progressive increase in inflammation or fibrosis. Smooth muscle actin (SMA) expression by stellate cells and CD34 expression by liver sinusoidal endothelial cells (LSECs) remained stable, consistent with the absence of progressive graft injury. Three subjects never exhibited DSA. However, three subjects showed intermittent de novo Class I DSA, four subjects showed persistent de novo Class II DSA and five subjects showed persistent pre-existing Class II DSA. Class II DSA was predominantly against donor DQ antigens, often of high mean fluorescence intensity (MFI), rarely of the IgG3 subclass, and often capable of binding C1q. CONCLUSION: Operationally tolerant pediatric liver transplant recipients maintain generally stable allograft histology in spite of apparently active humoral allo-immune responses. The absence of increased inflammation or progressive fibrosis suggests that a subset of liver allografts seem resistant to the chronic injury that is characteristic of antibody-mediated damage

Immunosuppression Withdrawal in Liver Transplant Recipients on Sirolimus

As conversion from calcineurin inhibitor (CNI) to sirolimus (SRL), an mTOR-inhibitor (mTOR-I), has been shown to enhance immunoregulatory profiles in liver transplant recipients (LTR), mTOR-I therapy might allow for increased success with immunosuppression withdrawal. Our aim was to determine if operational tolerance could be observed in LTR withdrawn from SRL and if blood/graft tolerance biomarkers were predictive of successful withdrawal. We performed a prospective trial of SRL monotherapy withdrawal in non-immune, non-viremic LTR > 3 years post-LT. Sirolimus was weaned over ~6 months and biopsies performed 12 months post-weaning or at concern for acute rejection (AR). Twenty-one LTR were consented; 6 were excluded due to subclinical AR on baseline biopsy or other reasons; 15 underwent weaning (age 61.3±8.8 yrs; LT to SRL weaning 6.7±3 yrs). Eight (53%) achieved operational tolerance (TOL). Of the 7 non-TOL, 6 had mild AR on biopsy near the end of weaning or at study end; 1 was removed due to liver cancer recurrence. At baseline preweaning, there were statistically higher blood tolerogenic dendritic cells, regulatory B cells, and cell phenotypes correlating with chronic antigen presentation in the TOL vs. non-TOL groups. At baseline preweaning, a previously identified biopsy gene signature accurately predicted TOL vs. non-TOL in 12/14 LTR. At study end, biopsy staining revealed statistically significant increases in antigen presenting cell:leukocyte pairings, Foxp3+CD4+ T cells, T-bet+CD8+ T cells, and lobular dendritic cells in the non-TOL group. CONCLUSION: This study is the first to evaluate IS withdrawal directly from mTOR-I therapy in LTR and achieved >50% operational tolerance. Pre-weaning blood/graft gene expression and PBMC profiling may be useful as predictors of successful mTOR-I therapy withdrawal. NCT0206294