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At least 19 recordsLinked to original sources
PubMed2005

Occurrence of heavy metal-resistance in microflora from serpentine soil of Andaman.

Serpentine soils collected from Saddle Hills, Chidyatapu and Rutland of Andaman Islands, India were analyzed for physico-chemical and microbiological characteristics and compared with those from adjacent non-serpentine localities. The serpentine soils contained high levels of nickel (1740.0-8033.4 mg/kg dry soil), cobalt (93.2-533.4 mg/kg dry soil) and chromium (302.9-4437.0 mg/kg dry soil), in addition to 62-152 g of iron and 37-60 g of magnesium per kg dry soil. Characteristically the serpentine soils showed low microbial density (6.2-11.3 x 10(6) colony forming unit/g soil) and activity (1.7-3.5 microg fluorescein/g dry soil/h) than non-serpentine outcrops. Serpentine microbial population was dominated by bacteria which represented 5.12 to 9.5 x 10(6) cfu/g of soil, while the fungal population ranged from 0.17 to 3.21 x 10(6) cfu/g of soil. A total of 342 (200 from serpentine and 142 from non-serpentine soils) isolates were compared for Ni, Co and Cr resistance. Serpentine microflora was in general, highly resistant than non-serpentine ones and showed a metal-resistance profile of Cr > Ni > Co. Amongst the serpentine isolates, 8 and 11 bacteria tolerated > 12.0 mM Ni and > 16.0 mM Cr respectively, while 6 fungal isolates showed a minimum inhibitory concentration (MIC) value > 8.0 mM Co. These 25 serpentine strains also showed co-resistance to Cu, Zn and Mn but were sensitive to Hg and Cd. The selected bacterial isolates were resistant to ampicillin, penicillin G and polymyxin B, whereas fungal strains showed resistance to amphotericin B, nystatin and fusidic acid.

Anti-Bacterial Agents↗
PubMed2005

Mutations in CAX1 produce phenotypes characteristic of plants tolerant to serpentine soils.

Plant tolerance of serpentine soils is potentially an excellent model for studying the genetics of adaptive variation in natural populations. A large-scale viability screen of Arabidopsis thaliana mutants on a defined nutrient solution with a low Ca(2+) : Mg(2+) ratio (1 : 24 mol : mol), typical of serpentine soils, yielded survivors with null alleles of the tonoplast calcium-proton antiporter CAX1. cax1 mutants have most of the phenotypes associated with tolerance to serpentine soils, including survival in solutions with a low Ca(2+) : Mg(2+) ratio; requirement for a high concentration of Mg(2+) for maximum growth; reduced leaf tissue concentration of Mg(2+); and poor growth performance on 'normal' levels of Ca(2+) and Mg(2+). A physiological model is proposed to explain how loss-of-function cax1 mutations could produce all these phenotypes characteristic of plants adapted to serpentine soils, why 'normal' plants are unable to survive on serpentine soil, and why serpentine-adapted plants are unable to compete on 'normal' soils.

Adaptation, Physiological↗
PubMed2005

Differences in growth characteristics and dynamics of elements absorbed in seedlings of three spruce species raised on serpentine soil in northern Japan.

BACKGROUND AND AIMS: Serpentine soils are characterized by the presence of heavy metals (Ni and Cr) and excess Mg; these elements often suppress plant growth. Picea glehnii is nevertheless distributed widely on serpentine soils in northern Japan. Growth characteristics were compared among P. glehnii, Picea jezoensis (distributed in the same region) and Picea abies (planted for timber production), and concentrations of elements in various tissues over time and the amount of ectomycorrhizal infection in short roots were evaluated. METHODS: Seedlings of three spruce species were planted in two types of experimental plots, comprising serpentine soil and brown forest (non-serpentine) soil, and these seedlings were grown for 3 years. Growth, ectomycorrhizal infection of short roots, and elemental composition of tissues were examined. KEY RESULTS: The total dry mass of P. glehnii planted on serpentine soil was almost the same as on brown forest soil, and a large number of needles survived to reach later age classes. By contrast, growth of P. jezoensis and P. abies in serpentine soil was significantly less than in brown forest soil, and needle shedding was accelerated. Moreover, roots of seedlings of P. glehnii on serpentine soil were highly infected with ectomycorrhiza, and the concentration of Ni in needles and roots of P. glehnii was the lowest of the three species. CONCLUSIONS: Picea glehnii has a high ability to maintain a low concentration of Ni, and the ectomycorrhizal infection may have the positive effect of excluding Ni. As a result, P. glehnii is more tolerant than the other spruce species to serpentine soil conditions.

Biomass↗
PubMed2002

Needle life span, photosynthetic rate and nutrient concentration of Picea glehnii, P. jezoensis and P. abies planted on serpentine soil in northern Japan.

We investigated the adaptation of three spruce species (Picea glehnii Masters, P. jezoensis Carr. and P. abies Karst.) to growth in northern Japan on serpentine soils (characterized by high concentrations of heavy metals and Mg, a low Ca/Mg ratio and low fertility) and fertile brown forest soils. Among species, seedling survival on serpentine soil was highest in P. glehnii. Shoot growth of P. glehnii was similar whether grown on serpentine or brown forest soil, whereas shoot growth of the other species was significantly less on serpentine soil than on brown forest soil. On serpentine soil, needle life span of P. glehnii was at least 3 years longer than that of the other two species. Needle area per shoot of P. glehnii was significantly higher on serpentine soil than on brown forest soil up to a shoot age of 8 years. In all three species, light-saturated photosynthetic rate (Pmax) decreased with needle age independently of soil type. However, on serpentine soil, Pmax in P. glehnii was higher, particularly in older needles, than in the other species. Furthermore, on serpentine soil, needle concentrations of nitrogen and phosphorus were higher in P. glehnii than in the other species. We conclude that P. glehnii is better adapted to serpentine soil than P. jezoensis and P. abies at least in part because of its greater needle life span and higher needle nutrient concentrations.

Asbestos, Serpentine↗
PubMed2004

QTL mapping for a trade-off between leaf and bud production in a recombinant inbred population of Microseris douglasii and M. bigelovii (Asteraceae, Lactuceae): a potential preadaptation for the colonization of serpentine soils.

The different response to growth on serpentine soil is a major autecological difference between the annual asteracean species Microseris douglasii and M. bigelovii, with nearly non-overlapping distribution ranges in California. Early flowering and seed set is regarded as a crucial character contributing to escape drought and thus is strongly correlated with survival and reproductive success on serpentine as naturally toxic soil. M. bigelovii (strain C94) from non-serpentine soil produces more leaves at the expense of bud production in the first growing phase than M. douglasii (B14) from serpentine soil. A QTL mapping study for this trade-off and for other growth-related traits was performed after six generations of inbreeding (F7) from a single interspecific hybrid between B14 and C94 on plants that were grown on serpentine and alternatively on normal potting soil. The trade-off is mainly correlated with markers on one map region on linkage group 03a (lg03a) with major phenotypic effects (phenotypic variance explained [PVE] = 18.8 - 31.7 %). Plants with the M. douglasii allele in QTL-B1 (QTL-NL1) produce more buds but fewer leaves in the first 119 days on both soil types. Three modifier QTL could be mapped for bud and leaf production. In one modifier (QTL-B2 = QTL-NL4) the M. douglasii allele is again associated with more buds but fewer leaves. QTL mapped for bud set in the F6 co-localize with QTL-B1 (major QTL) and QTL-B3. Two additional QTL for leaf length and red coloration of leaves could be mapped to one map region on lg03a. Co-localization of the two QTL loci with major phenotypic effects on bud and leaf production strongly suggests that a major genetic locus controls the trade-off between the two adaptive traits. The importance of mutational changes in major genes for the adaptation to stressful environments is discussed.

Adaptation, Physiological↗
PubMed2000

Effects of serpentine soil factors on Virginia pine (Pinus virginiana) seedlings.

Effects of simulated serpentine soil conditions (elevated Mg:Ca ratio and Ni concentration) on seedlings from populations of Virginia pine (Pinus virginiana Mill.) from serpentine and non-serpentine sites were evaluated in sand culture. We determined (1) how seedlings are affected by elevated Mg:Ca ratio and Ni concentrations, (2) if there are interactive effects between Mg:Ca ratio and Ni concentrations on seedling growth, needle pigment concentrations, and nutrition, and (3) if Virginia pine populations from serpentine areas are edaphic ecotypes. A Mg:Ca ratio of 5 and 50 microM Ni both reduced seedling growth compared with control seedlings grown in the presence of the standard Mg:Ca ratio of 0.5 and no Ni. Interactive effects between Mg:Ca ratio and Ni concentrations were highly significant for growth, foliar pigments, and needle and root elemental concentrations. Nickel-mediated reductions in growth and foliar pigment concentrations were less at the serpentine Mg:Ca ratio of 5 than at the standard (non-serpentine) Mg:Ca ratio of 0.5. Foliar N was reduced by Ni concentrations as low as 10 microM, and foliar and root K, Ca and P concentrations were significantly reduced by Ni concentrations above 25 microM, with greater reductions at a Mg:Ca ratio of 0.5 than at a Mg:Ca ratio of 5. There were no population x serpentine soil factor interactions for seedling growth, foliar pigment concentrations, or nutrition, suggesting that seedlings from trees growing on serpentine soils are not edaphic ecotypes. We conclude that serpentine conditions present at the site of seed collection have not resulted in the selection of edaphic ecotypes of Virginia pine with respect to Mg:Ca ratio and Ni concentration.

Asbestos, Serpentine↗
PubMed2004

Genetic diversity of bacterial communities of serpentine soil and of rhizosphere of the nickel-hyperaccumulator plant Alyssum bertolonii.

Serpentine soils are characterized by high levels of heavy metals (Ni, Co, Cr), and low levels of important plant nutrients (P, Ca, N). Because of these inhospitable edaphic conditions, serpentine soils are typically home to a very specialized flora including endemic species as the nickel hyperaccumulator Alyssum bertolonii. Although much is known about the serpentine flora, few researches have investigated the bacterial communities of serpentine areas. In the present study bacterial communities were sampled at various distances from A. bertolonii roots in three different serpentine areas and their genetic diversity was assessed by terminal restriction fragment length polymorphism (T-RFLP) analysis. The obtained results indicated the occurrence of a high genetic diversity and heterogeneity of the bacterial communities present in the different serpentine areas. Moreover, TRFs (terminal restriction fragments) common to all the investigated A. bertolonii rhizosphere samples were found. A new cloning strategy was applied to 27 TRFs that were sequenced and taxonomically interpreted as mainly belonging to Gram-positive and alpha-Proteobacteria representatives. In particular, cloned TRFs which discriminated between rhizosphere and soil samples were mainly interpreted as belonging to Proteobacteria representatives.

Bacteria↗
PubMed2005

Biosorption of cobalt by fungi from serpentine soil of Andaman.

Fungi belonging to Aspergillus, Mortierella, Paecilomyces, Penicillium, Pythium, Rhizopus and Trichoderma, isolated from serpentine soil of Andaman (India) were screened for cobalt-resistance. Eleven out of total 38 isolated fungi which tolerated > 6.0 mM Co(II) were evaluated for cobalt biosorption using dried mycelial biomass. Maximum Co(II)-loading (1036.5 microM/g, 60 min) was achieved with Mortierella SPS 403 biomass, which removed almost 50% of 4.0 mM cobalt from the aqueous solution. Co(II)-sorption kinetics of Mortierella SPS 403 biomass was fast and appreciable quantities of metal [562.5 microM/g] was adsorbed during first 10 min of incubation. The metal biosorption capacity of the isolate was accelerated with increasing cobalt concentration, while it was reverse with increase of initial biomass. The optimum pH and temperature for Co(II) removal were 7.0 and 30 degrees C, respectively. However, Co(II)-uptake was inhibited in presence of other metals (Pb, Cd, Cu, Ni, Cr and Zn). Freundlich adsorption isotherm appropriately describes Mortierella SPS 403 biomass as an efficient Co(II)-biosorbent.

Adsorption↗
PubMed2004

Aerobic chromate reduction by chromium-resistant bacteria isolated from serpentine soil.

A group of 34 chromium-resistant bacteria were isolated from naturally occurring chromium percolated serpentine soil of Andaman (India). These isolates displayed different degrees of chromate reduction under aerobic conditions. One of the 34 isolates identified as Bacillus sphaericus was tolerant to 800 mgl(-1) Cr(VI) and reduced > 80% Cr(VI) during growth. In Vogel Bonner broth, B. sphaericus cells (10(10) cells ml(-1)) reduced 62% of 20mg l(-1) of Cr(VI) in 48h with concomitant discoloring of yellow medium to white one. Reduction of chromate was pronounced by the addition of glucose and yeast extract as electron donors. In the presence of 4.0 g l(-1) of glucose, 20mg l(-1) of Cr(VI) was reduced to 2.45mg l(-1) after 96h of incubation. Optimum pH and temperature for reduction were 6.0 and 25 degrees C, respectively. Increase in cell density and initial Cr(VI) concentration increased chromate reduction but was inhibited by metal ions like, Ni2+, Co2+, Cd2+ and Pb2+. Experiments with cell-free extracts indicated that the soluble fraction of the cell was responsible for aerobic reduction of Cr(VI) by this organism.

Aerobiosis↗
PubMed2005

Reduction of hexavalent chromium by cell-free extract of Bacillus sphaericus AND 303 isolated from serpentine soil.

Cell-free extracts (CFEs) of chromium-resistant bacterium Bacillus sphaericus AND 303 isolated from serpentine soil of Andaman, India reduced Cr(VI) in in vitro condition, and the reductase activity was solely localized in the soluble cell-fractions (S12, S32, and S150). The enzyme was constitutive as the CFEs from cells grown in Cr(VI)-free and Cr(VI)-containing media reduced a more or less equal amount of Cr(VI). Optimum Cr(VI) reductase activity was obtained at an enzyme (S150) concentration equivalent to 4.56 mg protein/mL, 300 microM: Cr(VI) and pH 6.0 after 30 min incubation at 30 degrees C. The enzyme was heat labile; 80% of its activity was lost when exposed at 70 degrees C for 15 min. Kinetics of Cr(VI) reductase activity fit well with the linearized Lineweaver-Burk plot and showed a V(max) of 1.432 micromol Cr(VI)/mg protein/min and K(m) of 158.12 microM: Cr(VI). The presence of additional electron donors accelerated Cr(VI) reductase activity of CFE, and an increase of 28% activity over control was recorded with 1.0 microM: NADH. Heavy metal ions such as Ni(II), Cu(II), and Cd(II) were strong inhibitors of Cr(VI) reductase unlike that of 100 microM: Co(II), which retained 93% activity over control.

Anti-Bacterial Agents↗
PubMed2001

Characterization of nickel-resistant bacteria isolated from serpentine soil.

In the present study, heterotrophic nickel-resistant bacteria were isolated and characterized from three different serpentine outcrops in central Italy populated by the nickel-hyperaccumulating plant Alyssum bertolonii. Bacteria were isolated from the rhizosphere of the plant and from soil portions at various distances from the plant. The proportion of nickel-resistant cfu was higher in proximity to the plant than in free soil. A total of 138 isolates was collected and grouped into 47 different operational taxonomic units (OTUs) by means of amplified ribosomal DNA restriction analysis (ARDRA) and into 25 heavy-metal resistant phenotypes. The phylogenetic position of strains belonging to 20 OTUs, representing more than the 70% of the total isolates, was determined by 16S rDNA sequencing. These analyses showed that the most represented genera in all three different outcrops were Pseudomonas and Streptomyces. Pseudomonas strains were found to be predominant in the plant rhizosphere, whereas Streptomyces strains were mainly present in the soil.

Brassicaceae↗
PubMed2003

Rhizosphere characteristics of indigenously growing nickel hyperaccumulator and excluder plants on serpentine soil.

The role of rhizosphere processes in metal hyperaccumulation is largely unexplored and a matter of debate, related field data are virtually not available. We conducted a field survey of rhizosphere characteristics beneath the Ni hyperaccumulator Thlaspi goesingense Hálácsy and the metal-excluder species Silene vulgaris L. and Rumex acetosella L. growing natively on the same serpentine site. Relative to bulk soil and to the rhizosphere of the excluder species, we found significantly increased DOC and Ni concentrations in water extracts of T. goesingense rhizosphere, whereas exchangeable Ni was depleted due to excessive uptake of Ni. Chemical speciation analysis using the MINTEQA2 software package revealed that enhanced Ni solubility in Thlaspi rhizosphere is driven by the formation of Ni-organic complexes. Moreover, ligand-induced dissolution of Ni-bearing minerals is likely to contribute to enhanced Ni solubility. Increased Mg and Ca concentrations and pH in Thlaspi rhizosphere are consistent with ligand-induced dissolution of orthosilicates such as forsterite (Mg(2)SiO(4). Our field data reinforce the hypothesis that exudation of organic ligands may contribute to enhanced solubility and replenishment of metals in the rhizosphere of hyperaccumulating species.

Biodegradation, Environmental↗
PubMed2005

Comparison of 16S rRNA and 16S rDNA T-RFLP approaches to study bacterial communities in soil microcosms treated with chromate as perturbing agent.

Transcripts of ribosomal RNA have been used for assessing the structure and dynamics of active bacterial populations; however, it remains unclear whether the information provided by community profiling derived from RNA is different from that derived from DNA, particularly when a selective pressure is applied on the bacterial community. In the present work, terminal-restriction fragment length polymorphism (T-RFLP) community profiles based on DNA and RNA extracted from soil microcosms treated with a toxic concentration of chromate were compared. Microcosms of a nonpolluted agricultural soil and of a heavy-metal-rich soil (serpentine) were treated with chromate and DNA and RNA were extracted. T-RFLP analysis was performed on amplified and retro-amplified 16SrRNA gene sequences, and band profiles obtained from samples of DNA and of RNA were compared. Some of the T-RFLP bands, identified as peculiar peaks in the profiles, were cloned and sequenced for taxonomic interpretation. Results indicated that: (1) community profiles derived from RNA and DNA were partly overlapping; (2) there was a strong correlation between the dynamics shown by RNA- and DNA-based T-RFLP profiles; (3) chromate addition exerted a clear effect on both agricultural and serpentine soil bacterial communities, either at the DNA and at the RNA level; however, the profiles derived from RNA showed sharper differences between treated and control samples than that of DNA-based profiles.

Agriculture↗
PubMed2006

Soil calcium and plant disease in serpentine ecosystems: a test of the pathogen refuge hypothesis.

Ecologists have long sought mechanistic explanations for the patterns of plant distribution and endemism associated with serpentine soils. We conducted the first empirical test of the serpentine pathogen refuge hypothesis, which posits that the low levels of calcium found in serpentine soils provide associated plants with a refuge from attack by pathogens. We measured the range of soil calcium concentrations experienced by 16 wild population of California dwarf flax (Hesperolinon californicum) and experimentally recreated part of this range in the greenhouse by soaking serpentine soils in calcium chloride solutions of varying molarity. When flax plants grown in these soils were inoculated with spores of the rust fungus Melampsora lini we found a significant negative relationship between infection rates and soil calcium concentrations. This result refutes the pathogen refuge hypothesis and suggests that serpentine plants, by virtue of their association with low calcium soils, may be highly vulnerable to attack by pathogens. This interaction between plant nutrition and disease may in part explain demographic patterns associated with serpentine plant populations and suggests scenarios for the evolution of life history traits and the distribution of genetic resistance to infection in serpentine plant communities.

Analysis of Variance↗
PubMed2003

Mineral characteristics of leaves of plants from different phylogeny grown in various soil types in the temperate region.

The objective of this research was to analyze selected minerals in leaves of plants, belonging to 166 species growing in alluvial, low pH, brown forest and serpentine soils. Mineral characteristics of the soils involved were also determined. For the macronutrients, in trees grown in alluvial soil, N, P, Ca, and Mg concentrations of leaves were higher in recently evolved plants than in plants with a longer period of evolution; K concentration remained constant regardless of evolution. In grasses grown in alluvial soil, it was difficult to detect the general tendency of mineral concentration. N, P, and K concentrations in alluvial soil were closely related to those in low pH and serpentine soils. Ca concentration in alluvial soil was lower than that in low pH and serpentine soils. Mg concentration in alluvial soils was higher than that in low pH soils, while lower than that in serpentine soil. Therefore, N, P, and K accumulated according to the plant characteristics for these elements, while Ca and Mg accumulation was strongly affected by the soil properties. For the micronutrients, in trees, Fe and Mn remained constant regardless of evolution; Zn concentration was lower in recently-evolved plants than in plants with a longer period of evolution. In grasses, Fe, Mn, and Zn concentrations in Caryophyllids were high. Except for Caryophyllids, Fe and Cu concentrations remained constant. Mn concentration decreased with evolution, Zn concentration was higher in recently-evolved plants than in plants with a longer period of evolution.

Calcium↗