Phylogeography of microbial phototrophs in the dry valleys of the high Himalayas and Antarctica

High-elevation valleys in dry areas of the Himalayas are among the most extreme, yet least explored environments on Earth. These barren, rocky valleys are subjected to year-round temperature fluctuations across the freezing point and very low availability of water and nutrients, causing previous workers to hypothesize that no photoautotrophic life (primary producers) exists in these locations. However, there has been no work using modern biogeochemical or culture-independent molecular methods to test the hypothesis that photoautotrophs are absent from high Himalayan soil systems. Here, we show that although microbial biomass levels are as low as those of the Dry Valleys of Antarctica, there are abundant microbial photoautotrophs, displaying unexpected phylogenetic diversity, in barren soils from just below the permanent ice line of the central Himalayas. Furthermore, we discovered that one of the dominant algal clades from the high Himalayas also contains the dominant algae in culture-independent surveys of both soil and ice samples from the Dry Valleys of Antarctica, revealing an unexpected link between these environmentally similar but geographically very distant systems. Phylogenetic and biogeographic analyses demonstrated that although this algal clade is globally distributed to other high-altitude and high-latitude soils, it shows significant genetic isolation by geographical distance patterns, indicating local adaptation and perhaps speciation in each region. Our results are the first to demonstrate the remarkable similarities of microbial life of arid soils of Antarctica and the high Himalayas. Our findings are a starting point for future comparative studies of the dry valleys of the Himalayas and Antarctica that will yield new insights into the cold and dry limits to life on Earth.

Microbial activity and diversity during extreme freeze-thaw cycles in periglacial soils, 5400 m elevation, Cordillera Vilcanota, Perú

High-elevation periglacial soils are among the most extreme soil systems on Earth and may be good analogs for the polar regions of Mars where oligotrophic mineral soils abut with polar ice caps. Here we report on preliminary studies carried out during an expedition to an area where recent glacial retreat has exposed porous mineral soils to extreme, daily freeze-thaw cycles and high UV fluxes. We used in situ methods to show that inorganic nitrogen (NO(3) (-) and NH(4) (+)) was being actively cycled even during a period when diurnal soil temperatures (5 cm depth) ranged from -12 to 27 degrees C and when sub-zero, soil cooling rates reached 1.8 degrees C h(-1) (the most rapid soil cooling rates recorded to date). Furthermore, phylogenetic analyses of microbial phylotypes present at our highest sites (5410 m above sea level) showed the presence of nitrifying bacteria of the genus Nitrospira and newly discovered nitrite-oxidizing Betaproteobacteria. These soils were overwhelmingly dominated (>70% of phylotypes) by photosynthetic bacteria that were related to novel cyanobacteria previously found almost exclusively in other plant-free, high-elevation soils. We also demonstrated that soils from our highest sites had higher potential for mineralizing glutamate and higher microbial biomass than lower elevation soils that had been more recently covered by ice. Overall, our findings indicate that a diverse and robustly functioning microbial ecosystem is present in these previously unstudied high-elevation soils.

Developmental outcomes and cognitive functioning in infant and child heart transplant recipients

Pediatric heart transplantation has become a mainstay in the treatment of end-stage heart disease in infants and children. There is, however, sparse information on post-transplant developmental and cognitive functioning. At Loma Linda University Children's Hospital 223 infants have undergone heart transplantation surgery with a survival rate of 73% (n=165). This article reports on four areas of investigation of this cohort of infants. Infant development: Two studies were done utilizing the Bayley Scales of Infant Development (mean 100, S.D.+/-15). The first study (n=48) showed mean values within the normal range [Mental Development Index (MDI) 87; Psychomotor Developmental Index (PDI) 90]. The second study (n=23) showed developmental scores within normal limits in 4-8 month olds with a tendency for decline in development at 12-24 months (MDI 83, PDI 77). Child development: Ninty-one infant recipients were greater than 5 years old. Forty-five children were excluded because of long distances from the hospital, second transplantation, abnormal karyotype, primary language non-English, or invalid testing. The Wechsler Preschool and Primary Scale of Intelligence-Revised testing of 5-6-year-olds (n=23) showed a Full Scale IQ of 74, Performance IQ of 76, and Verbal IQ of 77. The Wechsler Intelligence Scale for Children-III testing of 7-10-year-olds (n=23) showed a Full Scale IQ of 86, Performance IQ of 89, and Verbal IQ of 86. The Wechsler Individual Achievement Test (mean 100, S.D.+/-15) yielded a Total Composite of 91, Mathematics Composite of 86, Language Composite of 98, and a Reading Composite of 94. Visual spatial skills: Visual motor integration (mean 100, S.D.+/-15) was evaluated in 5-10-year-olds with a mean of 87; however, 52% of the children had scores below 1 S.D. Subtests from the Wechsler scales that assess visual motor and visual spatial skills indicated significant deficits. Behavior: Younger children (n=33) demonstrated behaviors indicative of social isolation. Older children (n=36) showed behavior that was within the normal limits, but depression was noted in a significant number of them. Conclusions: Infant heart transplant recipients demonstrate IQ and achievement levels within the normal range, but there is a significant amount of variability with more children than would be expected scoring in the lower ranges. Children with heart transplantation are at risk for visual spatial skill deficits. Young children are at risk for social isolation while symptoms of depression are noted in older children.

An unusual type of mitochondrial DNA inheritance in the blue mussel Mytilus

In animals, mitochondrial DNA (mtDNA) inheritance is predominantly maternal. In a few cases incidental transmission of paternal mtDNA was observed and estimated to account for only 10(-4)-10(-3) of an individual's mtDNA content. In contrast, biparental inheritance is common in mussels of the genus Mytilus. Here we present direct evidence that sex and mtDNA inheritance are coupled in Mytilus. Females inherit mtDNA only from their mother, but they transmit it to both daughters and sons. Males inherit mtDNA from both parents, but they transmit to sons only the mtDNA they inherited from their father. In pair matings, this mtDNA inheritance pattern is associated with a strong sex-ratio bias. These findings establish a newly discovered type of cytoplasmic DNA transmission. We also present evidence that the phenomenon breaks down in interspecific hybrids.

Direct evidence for extensive paternal mitochondrial DNA inheritance in the marine mussel Mytilus

Inheritance of mitochondrial DNA in animals was thought to be strictly maternal. Recently, evidence for incidental paternal mtDNA leakage was obtained in hybrid crosses of Drosophila and mice. In mice, the frequency of paternal mtDNA contributions was estimated at 10(-4), compared with maternal contributions. The common occurrence in the marine mussel Mytilus of heteroplasmic individuals with two or more types of highly diverged mtDNA molecules was interpreted as strong evidence for biparental mtDNA inheritance by some, but not by others. We report here results from pair-matings involving two species of mussels, Mytilus edulis and Mytilus trossulus. Extensive contribution of paternal mtDNA, amounting to several orders of magnitude higher than that inferred for Drosophila or mice, was observed in both intra- and interspecific crosses.

Growth and Mortality of the Blue Mussel (Mytilus edulis) in Relation to Environmental Indexing

Comparative production estimates of selected species may provide indices of environmental quality, but so far there is little information on the extent to which production responses are mediated by genotypes. This study used a single source stock of blue mussels (Mytilus edulis) to explore differences between two bays. Test animals were held in suspension for 20 mo and growth and mortality observations of size-groups and of identified individuals were made at biweekly intervals. Average growth rates differed slightly between bays but mortality differences were marked and were the principle determinants of net production differences between the bays. Observed growth rates differed markedly between individuals but showed a striking consistency within individuals, indicative of genetic influence on this parameter. Because both mortality and growth interact with body size and season, it is clear that the estimated production levels and differences between bays would be influenced by the mixture of genotypes. We conclude that growth and mortality measures of M. edulis could provide sensitive environmental indices, but growth types in the test stock would need to be standardized. Key words: mussel; growth, mortality; environmental indices; genetic influence