Richness and diversity of microbial communities of the leaf litter of 4 plant species during 42 days incubation A: number of bands obtained from DGGE analysis of bacterial 16S rRNA gene PCR amplicons, B: Shannon’s index calculated from bacterial DGGE profiles, C: number of bands obtained from DGGE analysis of fungal 18S rRNA gene PCR amplicons, and D: Shannon’s index calculated from fungal DGGE profiles.

<p>The plant species <i>Baccaure ramiflora, Hevea brasiliensis, Pleioblastus amarus</i> and <i>Pometi tomentos</i> were denoted by Br, Hb, Pa and Pt, respectively.</p

DGGE profiles of fungal 18S rRNA gene amplicons derived from the leaf litter of the plant species A: <i>Baccaure ramiflora</i>, B: <i>Hevea brasiliensis</i>, C: <i>Pleioblastus amarus</i> and D: <i>Pometi tomentos</i>.

<p>The numbers of days of incubations are indicated. Each sampling day has two replicates of separate incubations denote by A and B. The arrows indicate the bands that have sequences affiliated to <i>Aspergillus</i> (day 1) and <i>Pleosporales</i> (day 42).</p

Annual mean values in (a) headwater stream dissolved organic carbon (DOC) concentrations, (b) riparian soil organic carbon (SOC) contents, (c) riparian water-soluble organic carbon (WSOC) contents, (d) riparian soil C:N ratio, and (e) temperature (mean±SD, n = 3) along an altitudinal gradient in the Wuyi Mountains of China (S1∶0–10 cm soil layer; S2∶10–25 cm soil layer; S3∶25–40 cm soil layer; EBF: evergreen broadleaf forest; CF: coniferous forest; SDF: subalpine dwarf forest; AM: alpine meadow; DOC: dissolved organic carbon; SOC: soil organic carbon; WSOC: water-soluble soil organic carbon). Significant differences between the means are marked with different letters.

<p>Annual mean values in (a) headwater stream dissolved organic carbon (DOC) concentrations, (b) riparian soil organic carbon (SOC) contents, (c) riparian water-soluble organic carbon (WSOC) contents, (d) riparian soil C:N ratio, and (e) temperature (mean±SD, n = 3) along an altitudinal gradient in the Wuyi Mountains of China (S1∶0–10 cm soil layer; S2∶10–25 cm soil layer; S3∶25–40 cm soil layer; EBF: evergreen broadleaf forest; CF: coniferous forest; SDF: subalpine dwarf forest; AM: alpine meadow; DOC: dissolved organic carbon; SOC: soil organic carbon; WSOC: water-soluble soil organic carbon). Significant differences between the means are marked with different letters.</p

Description of the four study sites located in the Wuyi Mountains, China.

<p>Note: AMT: annual mean temperature; AMP: annual mean precipitation. Datasets of annual mean temperature and annual mean precipitation are obtained from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0078973#pone.0078973-He1" target="_blank">[25]</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0078973#pone.0078973-Wang1" target="_blank">[26]</a>. Datasets of soil bulk density and soil pH are obtained from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0078973#pone.0078973-Bu1" target="_blank">[27]</a>. Datasets of litter biomass, microbial biomass and fine root biomass are obtained from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0078973#pone.0078973-He2" target="_blank">[28]</a>. Different lowercase letters indicate significant differences among four study sites in the same soil layer.</p

Annual mean data of stream DOC concentration and SOC character (mean±SD, n = 3).

<p>Different lowercase letters indicate significant differences among four study sites.</p

Map of headwater streams in the evergreen broadleaf forest (EBF), coniferous forest (CF), subalpine dwarf forest (SDF) and alpine meadow (AM) in the Wuyi Mountain National Nature Reserve of southeastern China (WNR, Wuyi Mountain National Nature Reserve; FJ, Fujian Province; JX, Jiangxi Province).

<p>Map of headwater streams in the evergreen broadleaf forest (EBF), coniferous forest (CF), subalpine dwarf forest (SDF) and alpine meadow (AM) in the Wuyi Mountain National Nature Reserve of southeastern China (WNR, Wuyi Mountain National Nature Reserve; FJ, Fujian Province; JX, Jiangxi Province).</p

Model of Hormesis and Its Toxicity Mechanism Based on Quorum Sensing: A Case Study on the Toxicity of Sulfonamides to <i>Photobacterium phosphoreum</i>

During the past two decades, the phenomenon of hormesis has gained increasing recognition in environmental and toxicological communities. However, the mechanistic understanding of hormesis, to date, is extremely limited. Herein is proposed a novel parametric model with a mechanistic basis and two model-based parameters for hormesis that was successfully applied to the hormetic dose–response observed in the chronic toxicity of sulfonamides on <i>Photobacterium phosphoreum</i>. On the basis of the methods of molecular docking and quantitative structure–activity relationships (QSARs), we proposed a mechanistic hypothesis for hormesis that introduces for the first time the concept of quorum sensing in toxicological studies and explains the mechanism at the level of the receptors. The mechanistic hypothesis stated that (1) specific target binding like interaction with LuxR may contribute to transcriptional activation leading to enhanced luciferase activity at low dose exposure of sulfonamides, and (2) as the dose of sulfonamides increases, more sulfonamides competitively bind to dihydropteroate synthase, which inhibit the biosynthesis of folic acid and thus provoke toxicity. This mechanistic hypothesis, which explains both the dose-dependent and time-dependent features of hormesis, could give new insight into the mechanistic study of hormesis

Relationship of SOC in bulk soil with soil moisture (a), coarse particulate organic matter content (b) and MWD (c).

<p>Relationship of SOC in bulk soil with soil moisture (a), coarse particulate organic matter content (b) and MWD (c).</p

Distribution of coarse particulate organic matter (cPOM), microaggregates within the macroaggregates (mM), macroaggregate occluded in silt and clay particles (scM), microaggregates (Micros) and silt and clay particles (SC), mean weight diameter (MWD) and soil organic carbon in soil samples collected at evergreen broad-leaf forest (EBF), coniferous forest (CF), sub-alpine dwarf forest (DF) and alpine meadow (AM) on Wuyi Mountain, China (mean ± standard error, n = 4).

<p>Distribution of coarse particulate organic matter (cPOM), microaggregates within the macroaggregates (mM), macroaggregate occluded in silt and clay particles (scM), microaggregates (Micros) and silt and clay particles (SC), mean weight diameter (MWD) and soil organic carbon in soil samples collected at evergreen broad-leaf forest (EBF), coniferous forest (CF), sub-alpine dwarf forest (DF) and alpine meadow (AM) on Wuyi Mountain, China (mean ± standard error, n = 4).</p

Distribution of organic carbon in coarse particulate organic matter (cPOM), microaggregates within the macroaggregates (mM), macroaggregate-occluded silt and clay particles (scM), microaggregates (Micro) and silt and clay (SC) particles of samples collected at an evergreen broad-leaf forest (EBF), coniferous forest (CF), sub-alpine dwarf forest (DF) and alpine meadow (AM) on Wuyi Mountain, China in the 0–10 cm layer (a) and 10–25 cm layer (b).

<p>Different letters for the sane vegetation indicate significant differences among the different size fractions of soil aggregates at P<0.05 (n = 4).</p