The volatile compound 2,3-butanediol, which is produced by certain strains of root-associated bacteria, consists of three stereoisomers, namely, two enantiomers (2R,3R- and 2S,3S-butanediol) and one meso compound (2R, 3S-butanediol). The ability of 2,3-butanediol to induce plant resistance against pathogenic fungi and bacteria has been investigated; however, little is known about its effects on induced resistance against viruses in plants. To investigate the effects of 2,3-butanediol on plant systemic defense against viruses, we evaluated the disease control capacity of each of its three stereoisomers in pepper. Specifically, we investigated the optimal concentration of 2,3-butanediol to use for disease control against Cucumber mosaic virus and Tobacco mosaic virus in the greenhouse and examined the effects of drench application of these compounds in the field. In the field trial, treatment with 2R,3R-butanediol and 2R,3-Sbutanediol significantly reduced the incidence of naturally occurring viruses compared with 2S, 3S-butanediol and control treatments. In addition, 2R, 3R-butanediol treatment induced the expression of plant defense marker genes in the salicylic acid, jasmonic acid, and ethylene signaling pathways to levels similar to those of the benzothiadiazole-treated positive control. This study reports the first field trial showing that specific stereoisomers of 2,3-butanediol trigger plant immunity against multiple viruses.

2,3-BTD activates NK cells cytotoxicity by NKG2D/NCRs pathways.

Plant growth-promoting rhizobacteria, in association with plant roots, can trigger induced systemic resistance (ISR). Considering that low-molecular weight volatile hormone analogues such as methyl jasmonate and methyl salicylate can trigger defense responses in plants, we examined whether volatile organic compounds (VOCs) associated with rhizobacteria can initiate ISR. In Arabidopsis seedlings exposed to bacterial volatile blends from Bacillus subtilis GB03 and Bacillus amyloliquefaciens IN937a, disease severity by the bacterial pathogen Erwinia carotovora subsp. carotovora was significantly reduced compared with seedlings not exposed to bacterial volatiles before pathogen inoculation. Exposure to VOCs from rhizobacteria for as little as 4 d was sufficient to activate ISR in Arabidopsis seedlings. Chemical analysis of the bacterial volatile emissions revealed the release of a series of low-molecular weight hydrocarbons including the growth promoting VOC (2R,3R)-(-)-butanediol. Exogenous application of racemic mixture of (RR) and (SS) isomers of 2,3-butanediol was found to trigger ISR and transgenic lines of B. subtilis that emitted reduced levels of 2,3-butanediol and acetoin conferred reduced Arabidopsis protection to pathogen infection compared with seedlings exposed to VOCs from wild-type bacterial lines. Using transgenic and mutant lines of Arabidopsis, we provide evidence that the signaling pathway activated by volatiles from GB03 is dependent on ethylene, albeit independent of the salicylic acid or jasmonic acid signaling pathways. This study provides new insight into the role of bacteria VOCs as initiators of defense responses in plants.

CcpA, the repressor/activator mediating carbon catabolite repression and glucose activation in many Gram-positive bacteria, has been purified from Bacillus megaterium after fusing it to a His tag. CcpA-his immobilized on a Ni-NTA resin specifically interacted with HPr phosphorylated at seryl residue 46. HPr, a phospho-carrier protein of the phosphoenolpyruvate: glycose phosphotransferase system (PTS), can be phosphorylated at two different sites: (i) at His-15 in a PEP-dependent reaction catalysed by enzyme I of the PTS; and (ii) at Ser-46 in an ATP-dependent reaction catalysed by a metabolite-activated protein kinase. Neither unphosphorylated HPr nor HPr phosphorylated at His-15 nor the doubly phosphorylated HPr bound to CcpA. The interaction with seryl-phosphorylated HPr required the presence of fructose 1,6-bisphosphate. These findings suggest that carbon catabolite repression in Gram-positive bacteria is a protein kinase-triggered mechanism. Glycolytic intermediates, stimulating the corresponding protein kinase and the P-ser-HPr/CcpA complex formation, provide a link between glycolytic activity and carbon catabolite repression. The sensitivity of this complex formation to phosphorylation of HPr at His-15 also suggests a link between carbon catabolite repression and PTS transport activity.

旨在应用自杀质粒重组技术,构建阴沟肠杆菌乳酸脱氢酶突变株,为进一步提高乙偶姻的产量和扩大菌株选择范围奠定基础。利用双酶切的方法将同源片段插入到自杀质粒pKR6K中,构建出ldh基因敲除质粒,然后利用细菌接合的方法敲除E. cloacae的ldh基因。成功克隆出两段E. cloacae乳酸脱氢酶基因的同源序列,长度分别为526 bp,通过序列比对分析,E. cloacae乳酸脱氢酶基因序列相似性为100%。通过对E. cloacae进行乳酸脱氢酶基因的敲除,成功构建一株ldh缺失重组菌株E. cloacae△ldh,同时2,3-丁二醇提高6.8%,乙酸提高了24.3%。E. cloacae乳酸脱氢酶缺失工程菌株构建成功,对利用微生物法工业化生产乙偶姻奠定基础。

There is increasing interest in production of transportation fuels and commodity chemicals from lignocellulosic biomass, most desirably through biological fermentation. Considerable effort has been expended to develop efficient biocatalysts that convert sugars derived from lignocellulose directly to value-added products. Glucose, the building block of cellulose, is the most suitable fermentation substrate for industrial microorganisms such as Escherichia coli, Corynebacterium glutamicum, and Saccharomyces cerevisiae. Other sugars including xylose, arabinose, mannose, and galactose that comprise hemicellulose are generally less efficient substrates in terms of productivity and yield. Although metabolic engineering including introduction of functional pentose-metabolizing pathways into pentose-incompetent microorganisms has provided steady progress in pentose utilization, further improvements in sugar mixture utilization by microorganisms is necessary. Among a variety of issues on utilization of sugar mixtures by the microorganisms, recent studies have started to reveal the importance of sugar transporters in microbial fermentation performance. In this article, we review current knowledge on diversity and functions of sugar transporters, especially those associated with pentose uptake in microorganisms. Subsequently, we review and discuss recent studies on engineering of sugar transport as a driving force for efficient bioconversion of sugar mixtures derived from lignocellulose.

Glucose is the classical carbon source that is used to investigate the transport, metabolism, and regulation of nutrients in bacteria. Many physiological phenomena like nutrient limitation, stress responses, production of antibiotics, and differentiation are inextricably linked to nutrition. Over the years glucose transport systems have been characterized at the molecular level in more than 20 bacterial species. This review aims to provide an overview of glucose uptake systems found in the eubacterial kingdom. In addition, it will highlight the diverse and sophisticated regulatory features of glucose transport systems.