Perchlorate biodegradation in contaminated soils and the deep unsaturated zone

In the United States, perchlorate has been officially recognized as an environmental contaminant. In Israel, widespread perchlorate contamination has been found in the 40-m deep vadose zone near an ammonium perchlorate manufacturing plant north of Tel Aviv, above the central part of Israel's coastal aquifer, with peak concentrations of 1200 mg kg_sediment^?1. In this study, we examined the perchlorate-reduction potential by native microbial communities along this deep contaminated vadose zone profile. We analyzed the effect of various concentrations of nitrate on perchlorate reduction and determined whether perchlorate concentrations in the profile are toxic to the native microbial population. All experiments were performed in soil slurries with sediments taken from the contaminated site. Perchlorate was reduced to chloride in three (1, 15 and 35 m) of the four examined sediment samples taken from different depths (1, 15, 20, and 35 m below surface). No activity was observed in the sediment sample from 20 m below land surface, suggesting low viable microbial communities and water content, and high perchlorate concentrations. In the presence of nitrate, the lag time for perchlorate degradation was inversely correlated to nitrate concentration. We found no perchlorate degradation as long as nitrate was present in the system, and perchlorate degradation initiated only after all the nitrate had been reduced. Nitrate-reduction rates were correlated to the initial concentrations of nitrate and no lag period was observed for nitrate reduction. Viable microbial populations were observed at both high concentrations (10,000 mg l^?1 and 20,000 mg l^?1) and with no addition of perchlorate, at levels of 2.35 × 10⁵, 4.01 × 10⁵, and 3.41 × 10³ CFU ml^?1, respectively; these results were well correlated to those found by PCR amplification analysis of chlorite dismutase. We suggest that the microbial community has adapted to the conditions of high perchlorate concentrations in the unsaturated zone over 30 years of exposure. When no external carbon source was added to the slurry of soil from land surface, all perchlorate was removed after 134 days of incubation. The average perchlorate-reduction rate using natural organic matter as a carbon source was 0.45 mg day^?1, while the average rate using acetate as an external carbon source was 7.2 mg day^?1.     

Early domesticated fig in the Jordan Valley

It is generally accepted that the fig tree was domesticated in the Near East some 6500 years ago. Here we report the discovery of nine carbonized fig fruits and hundreds of drupelets stored in Gilgal I, an early Neolithic village, located in the Lower Jordan Valley, which dates to 11,400 to 11,200 years ago. We suggest that these edible fruits were gathered from parthenocarpic trees grown from intentionally planted branches. Hence, fig trees could have been the first domesticated plant of the Neolithic Revolution, which preceded cereal domestication by about a thousand years.     

Microbial changes occurring at the sediment-water interface in an intensively stocked and fed fish pond

The microbial changes occurring in the upper 1 cm of the solid sediment surface in intensively fed and aerated fish ponds located in northern Israel were examined. The bacterial groups enumerated included: total aerobes, total anaerobes, sulfate and iron reducing bacteria, ammonia and nitrite oxidizing bacteria, acid forming bacteria, and denitrifying bacteria. With the exception of the nitrifying bacteria, large microbial populations were observed in the pond sediment even prior to fish stocking. All the different groups enumerated displayed a rapid change in number during the first 2–8 days following fish stocking, and a subsequent approach toward a steady state. Since both microbial and chemical steady states were approached within a relatively short period of time, it does not appear that these components of the sediment are related to the inhibition of fish growth occurring 50–70 days after fish stocking. While the practice of pond draining and air drying the sediment does oxidize some of the accumulated organic material, it does not appear to affect the resident microbial flora significantly to an extent that could decrease the rate of reestablishment of the microbial community. Therefore, upon establishment of anaerobic conditions a large microbiological community is present capable of mediating the chemical reduction of SO₄^2? to H₂S, or other transformations resulting in products which contribute to fish growth inhibition commonly observed in such intensively stocked and fed fish ponds.     

Independent selection for seed free tryptophan content and vernalization response in chickpea domestication

Chickpea shows a distinct domestication trajectory vis‐a‐vis pod dehiscence and growth cycle mediated by vernalization insensitivity compared with its companion Near Eastern legumes. Our objectives were: (i) to map the quantitative trait loci (QTLs) associated with vernalization response and seed free tryptophan in domesticated × wild chickpea progeny and (ii) estimate the genetic correlation between vernalization response and free tryptophan content. A domesticated × wild chickpea cross was used to document phenotypic segregation in both traits and to construct a skeletal genetic map for QTL detection. A number of vernalization response and seed free tryptophan content QTLs were documented in both F₂ and F₃ generations. No significant genetic correlation between these two traits was observed. Epistatic relationship between two free tryptophan loci was documented. It is evident that selection for high seed tryptophan is easier to accomplish relative to selection for vernalization insensitivity. This suggests that the two traits were selected independently in antiquity, thereby corroborating earlier claims for conscious selection processes associated with chickpea domestication.     

Host immune system gene targeting by a viral miRNA

Virally encoded microRNAs (miRNAs) have recently been discovered in herpesviruses. However, their biological roles are mostly unknown. We developed an algorithm for the prediction of miRNA targets and applied it to human cytomegalovirus miRNAs, resulting in the identification of the major histocompatibility complex class I-related chain B (MICB) gene as a top candidate target of hcmv-miR-UL112. MICB is a stress-induced ligand of the natural killer (NK) cell activating receptor NKG2D and is critical for the NK cell killing of virus-infected cells and tumor cells. We show that hcmv-miR-UL112 specifically down-regulates MICB expression during viral infection, leading to decreased binding of NKG2D and reduced killing by NK cells. Our results reveal a miRNA-based immunoevasion mechanism that appears to be exploited by human cytomegalovirus.