Discovery of a New Natural Product and a Deactivation of a Quorum Sensing System by Culturing a “Producer” Bacterium With a Heat-Killed “Inducer” Culture

Herein we describe a modified bacterial culture methodology as a tool to discover new natural products via supplementing actinomycete fermentation media with autoclaved cultures of “inducer” microbes. Using seven actinomycetes and four inducer microbes, we detected 28 metabolites that were induced in UHPLC-HRESIMS-based analysis of bacterial fermentations. Metabolomic analysis indicated that each inducer elicited a unique response from the actinomycetes and that some chemical responses were specific to each inducer-producer combination. Among these 28 metabolites, hydrazidomycin D, a new hydrazide-containing natural product was isolated from the pair Streptomyces sp. RKBH-B178 and Mycobacterium smegmatis. This result validated the effectiveness of the strategy in discovering new natural products. From the same set of induced metabolites, an in-depth investigation of a fermentation of Streptomyces sp. RKBH-B178 and autoclaved Pseudomonas aeruginosa led to the discovery of a glucuronidated analog of the pseudomonas quinolone signal (PQS). We demonstrated that RKBH-B178 is able to biotransform the P. aeruginosa quorum sensing molecules, 2-heptyl-4-quinolone (HHQ), and PQS to form PQS-GlcA. Further, PQS-GlcA was shown to have poor binding affinity to PqsR, the innate receptor of HHQ and PQS

Responses of Vegetation Growth to Climatic Factors in Shule River Basin in Northwest China: A Panel Analysis

The vegetation response to climatic factors is a hot topic in global change research. However, research on vegetation in Shule River Basin, which is a typical arid region in northwest China, is still limited, especially at micro scale. On the basis of Moderate-resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data and daily meteorological data, employing panel data models and other mathematical models, the aim of this paper is to reveal the interactive relationship between vegetation variation and climatic factors in Shule River Basin. Results show that there is a widespread greening trend in the whole basin during 2000–2015, and 80.28% of greening areas (areas with vegetation improvement) are distributed over upstream region, but the maximum vegetation variation appears in downstream area. The effects of climate change on NDVI lag about half to one month. The parameters estimated using panel data models indicate that precipitation and accumulated temperature have positive contribution to NDVI. With every 1-mm increase in rainfall, NDVI increases by around 0.223‰ in upstream area and 0.6‰ in downstream area. With every 1-°C increase in accumulated temperature, NDVI increases by around 0.241‰ in upstream area and 0.174‰ in downstream area. Responses of NDVI to climatic factors are more sensitive when these factors are limiting than when they are not limiting. NDVI variation has performance in two seasonal and inter-annual directions, and the range of seasonal change is far more than that of inter-annual change. The inverted U-shaped curve of the variable intercepts reflects the seasonal change. Our results might provide some scientific basis for the comprehensive basin management

Protective effect of glycyrrhizin, a direct HMGB1 inhibitor, on focal cerebral ischemia/reperfusion-induced inflammation, oxidative stress, and apoptosis in rats.

AIM: Glycyrrhizin (GL) has been reported to protect against ischemia and reperfusion (I/R)-induced injury by inhibiting the cytokine activity of high mobility group box 1 (HMGB1). In the present study, the protective effects of GL against I/R injury, as well as the related molecular mechanisms, were investigated in rat brains. METHODS: Focal cerebral I/R injury was induced by intraluminal filamentous occlusion of the middle cerebral artery (MCA) in Male Sprague-Dawley rats. GL alone or GL and rHMGB1 were administered intravenously at the time of reperfusion. Serum levels of HMGB1 and inflammatory mediators were quantified via enzyme-linked immunosorbent assay (ELISA). Histopathological examination, immunofluorescence, RT-PCR and western blotting analyses were performed to investigate the protective and anti-apoptotic effects and related molecular mechanisms of GL against I/R injury in rat brains. RESULTS: Pre-treatment with GL significantly reduced infarct volume and improved the accompanying neurological deficits in locomotor function. The release of HMGB1 from the cerebral cortex into the serum was inhibited by GL administration. Moreover, pre-treatment with GL alleviated apoptotic injury resulting from cerebral I/R through the inhibition of cytochrome C release and caspase 3 activity. The expression levels of inflammation- and oxidative stress-related molecules including TNF-α, iNOS, IL-1β, and IL-6, which were over-expressed in I/R, were decreased by GL. P38 and P-JNK signalling were involved in this process. All of the protective effects of GL could be reversed by rHMGB1 administration. CONCLUSIONS: GL has a protective effect on ischemia-reperfusion injury in rat brains through the inhibition of inflammation, oxidative stress and apoptotic injury by antagonising the cytokine activity of HMGB1

The protective effect of GL on I/R-induced infarct volume and apoptosis injury is HMGB1 dependent.

<p>A) Brain infarction induced by right MCA occlusion was evaluated by TTC staining from rats pre-treated with 4 mg/kg GL with or without 100 µg recombinant HMGB1, and the infarct volumes 48 h after reperfusion were quantified using NIH image software. B) Representative photomicrographs show TUNEL staining for apoptotic cells in rat brains at 48 h after reperfusion in the sham, NS, GL and GL+rHMGB1 groups. Effects on the severity of cerebral apoptosis are shown in an average quantitative analysis of the number of TUNEL-positive cells. C) Representative blots showing the effects of GL with or without rHMGB1 treatment on Cytochrome c translocation between the mitochondrial and cytosolic fractions. D) Effects of GL with or without rHMGB1 treatment on caspase-3 activity in areas at the risk zone of cerebral tissues at 48 h after reperfusion. Values are means±SEM, n = 8 for each group. *P<0.05, **P<0.01 (t test).</p

Expression of inflammation- and oxidative stress-related molecules in the brain and serum of MCA-occluded rats at 48 h after reperfusion.

<p>A) Representative blots showing the effects of GL with or without rHMGB1 treatment on mRNA expression levels of pro-inflammatory and oxidative stress markers: TNF-α, iNOS, IL-1β, COX-2 and IL-6. GAPDH was used as a loading control. The bar graph showing semi-quantitative densitometric analysis summarises the fold change of TNF-α, iNOS, IL-1β, COX-2 and IL-6 expression in each group. B) Serum concentrations of TNF-α, iNOS, IL-1β, COX-2 and IL-6 at 48 h after I/R in each groups are determined. Values are means±SEM, n = 8 for each group. *P<0.05, **P<0.01 (t test).</p

The neuroprotective effect of GL against cerebral I/R injury in rats.

<p>A) Cerebral infarction induced by MCA occlusion was evaluated 48 h after reperfusion by TTC staining of brain slices from rats treated with different doses of GL or NS. Sham-operated rats showed no infarction or TTC staining. The infarct volumes were quantified using computerised image analysis. B) Neurological scoring was carried out according to the categories described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0089450#s2" target="_blank">Materials and Methods</a>. C) Neurological deficits in rats after MCA occlusion were examined using the rota-rod test. In the rota-rod test, trials were performed at 3 different speeds, and the time intervals running on the rod were determined for each rat after reperfusion. Values are means±SEM, n = 8 for each group. *P<0.05, **P<0.01 (t test).</p

The antioxidant effects of GL are HMGB1 dependent.

<p>A) Fluorescent images after incubation with DHE showing superoxide levels in the I/R brain (red). Quantitative measurements of the fluorescence intensity indicated a significant change in the 4 mg/kg GL-treated group with or without rHMGB1, compared with the saline-treated I/R (NS) group. B) Representative photomicrographs showing 3-NT formation in the ischemic brain (green). Data from image analysis also indicated a significant change in the 4 mg/kg GL-treated group with or without rHMGB1, compared with the saline-treated I/R (NS) group. Bar = 50 µm. C) The effects of 4 mg/kg GL with or without rHMGB1 on MDA content in rat brains after I/R. Values are means±SEM, n = 8 for each group. *P<0.05, **P<0.01 (t test).</p

Representative blots showing the effects of GL with or without rHMGB1 treatment on phosphorylated (p) and total (t) p38, JNK, and ERK expression.

<p>Each blot shown is representative of 3 experiments with similar results. The bar graph showing semi-quantitative densitometric analysis summarises the fold change in phosphorylated to total p38, JNK and ERK in each group. Values are means±SEM, n = 8 for each group. *P<0.05, **P<0.01 (t test).</p

A Silent Operon of Photorhabdus luminescens Encodes a Prodrug Mimic of GTP

Drug-resistant Gram-negative bacteria have become the major problem driving the antimicrobial resistance crisis. Searching outside the overmined actinomycetes, we focused on Photorhabdus , gut symbionts of enthomopathogenic nematodes that carry up to 40 biosynthetic gene clusters coding for secondary metabolites. </jats:p