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Guirong Tang, Qiong Li, Shenghui Xing, Ningning Li, Zheng Tang, Liangliang Yu, Junhui Yan, Xuan Li, Li Luo
Agrobacterium tumefaciens infects and causes crown galls in dicot plants by transferring T-DNA from the Ti plasmid to the host plant via a type IV secretion system (T4SS). This process requires appropriate environmental conditions, certain plant secretions and bacterial regulators. In our previous work, a member of the LysR family of transcriptional regulators (LsrB) in Sinorhizobium meliloti was found to modulate its symbiotic interactions with the host plant alfalfa. However, the function of its homologue in A...
March 16, 2018: Molecular Plant-microbe Interactions: MPMI
Anne-Marie Garnerone, Fernando Sorroche, Lan Zou, Céline Mathieu-Demazière, Chang Fu Tian, Catherine Masson-Boivin, Jacques Batut
An ongoing signal exchange fine-tunes the symbiotic interaction between rhizobia and legumes, ensuring the establishment and maintenance of mutualism. In a recently identified regulatory loop, endosymbiotic S. meliloti exert a negative feedback on root infection in response to unknown plant cues. Upon signal perception, three bacterial Adenylate Cyclases (ACs) of the inner membrane, CyaD1, CyaD2 and CyaK, synthesize the second messenger cAMP that, together with the cAMP-dependent Clr transcriptional activator, activates the expression of genes involved in root infection control...
March 12, 2018: Journal of Bacteriology
Isabel M López-Lara, Joaquina Nogales, Ángel Pech-Canul, Nieves Calatrava-Morales, Lydia M Bernabéu-Roda, Paloma Durán, Virginia Cuéllar, José Olivares, Laura Alvarez, Diana Palenzuela-Bretones, Manuel Romero, Stephan Heeb, Miguel Cámara, Otto Geiger, María J Soto
Surface motility and biofilm formation are behaviours which enable bacteria to infect their hosts and are controlled by different chemical signals. In the plant symbiotic alpha-proteobacterium Sinorhizobium meliloti, the lack of long-chain fatty acyl-coenzyme A synthetase activity (FadD) leads to increased surface motility, defects in biofilm development, and impaired root colonization. In this study, analyses of lipid extracts and volatiles revealed that a fadD mutant accumulates 2-tridecanone (2-TDC), a methylketone known as a natural insecticide...
February 28, 2018: Environmental Microbiology
Marta Robledo, Ana M Matia-González, Natalia I García-Tomsig, José I Jiménez-Zurdo
The identification of the protein partners of bacterial small noncoding RNAs (sRNAs) is essential to understand the mechanistic principles and functions of riboregulation in prokaryotic cells. Here, we describe an optimized affinity chromatography protocol that enables purification of in vivo formed sRNA-protein complexes in Sinorhizobium meliloti, a genetically tractable nitrogen-fixing plant symbiotic bacterium. The procedure requires the tagging of the desired sRNA with the MS2 aptamer, which is affinity-captured by the MS2-MBP protein conjugated to an amylose resin...
2018: Methods in Molecular Biology
Claus Lang, Lucinda S Smith, Sharon R Long
The formation of nitrogen fixing root nodules by Medicago truncatula and Sinorhizobium meliloti requires communication between both organisms and coordinated differentiation of plant and bacterial cells. After an initial signal exchange, the bacteria invade the tissue of the growing nodule via plant-derived tubular structures, called infection threads. The bacteria are released from the infection threads into invasion-competent plant cells, where they differentiate into nitrogen-fixing bacteroids. Both organisms undergo dramatic transcriptional, metabolic and morphological changes during nodule development...
2018: Frontiers in Plant Science
María J Torres, Sergio Avila, Eulogio J Bedmar, María J Delgado
The alfalfa endosymbiont Ensifer meliloti strain1021 is known to be an incomplete denitrifier due to its inability to grow anoxically using nitrate as respiratory substrate to produce ATP and grow under anoxic conditions. Although this bacterium contains and expresses the complete set of denitrification genes napEFDABC, nirK, norECBQD and nosRZDFYLX encoding the periplasmic nitrate reductase (Nap), Cu-containing nitrite reductase (NirK), c-type nitric oxide (cNor) and nitrous oxide reductase (Nos), respectively, the reasons of its inability to grow under anoxic conditions are still very poorly understood...
February 16, 2018: FEMS Microbiology Letters
Bert van Loo, Markus Schober, Eugene Valkov, Magdalena Heberlein, Erich Bornberg-Bauer, Kurt Faber, Marko Hyvönen, Florian Hollfelder
Hydrolysis of organic sulfate esters proceeds by two distinct mechanisms, water attacking at either sulfur (S-O bond cleavage) or carbon (C-O bond cleavage). In primary and secondary alkyl sulfates attack at carbon is favored, whereas in aromatic sulfates and sulfated sugars attack at sulfur is preferred. This mechanistic distinction is mirrored in the classification of enzymes that catalyze sulfate ester hydrolysis: arylsulfatases catalyze S-O cleavage in sulfate sugars and arylsulfates and alkyl sulfatases break the C-O bond of alkyl sulfates...
February 16, 2018: Journal of Molecular Biology
Amrita B Hazra, David P Ballou, Michiko E Taga
Vitamin B12 (cobalamin) is an essential micronutrient for humans that is synthesized only by a subset of bacteria and archaea. The aerobic biosynthesis of 5,6-dimethylbenzimidazole, the lower axial ligand of cobalamin is catalyzed by the "flavin destructase" enzyme BluB, which fragments reduced flavin mononucleotide following its reaction with oxygen to yield this ligand. BluB shares sequence and structural similarity with the flavin oxidoreductase superfamily, yet the flavin destruction process has remained elusive...
February 19, 2018: Biochemistry
Liana T Burghardt, Brendan Epstein, Joseph Guhlin, Matt S Nelson, Margaret R Taylor, Nevin D Young, Michael J Sadowsky, Peter Tiffin
Assays to accurately estimate relative fitness of bacteria growing in multistrain communities can advance our understanding of how selection shapes diversity within a lineage. Here, we present a variant of the "evolve and resequence" approach both to estimate relative fitness and to identify genetic variants responsible for fitness variation of symbiotic bacteria in free-living and host environments. We demonstrate the utility of this approach by characterizing selection by two plant hosts and in two free-living environments (sterilized soil and liquid media) acting on synthetic communities of the facultatively symbiotic bacterium Ensifer meliloti We find ( i ) selection that hosts exert on rhizobial communities depends on competition among strains, ( ii ) selection is stronger inside hosts than in either free-living environment, and ( iii ) a positive host-dependent relationship between relative strain fitness in multistrain communities and host benefits provided by strains in single-strain experiments...
February 16, 2018: Proceedings of the National Academy of Sciences of the United States of America
Jie Cai, Lan-Yue Zhang, Wei Liu, Ye Tian, Jin-Song Xiong, Yi-Han Wang, Ru-Jie Li, Hao-Ming Li, Jiangqi Wen, Kirankumar S Mysore, Thomas Boller, Zhi-Ping Xie, Christian Staehelin
Establishment of symbiosis between legumes and nitrogen-fixing rhizobia depends on bacterial Nod factors (NFs) that trigger symbiosis-related NF signaling in host plants. NFs are modified oligosaccharides of chitin with a fatty acid moiety. NFs can be cleaved and inactivated by host enzymes, such as MtNFH1 (MEDICAGO TRUNCATULA NOD FACTOR HYDROLASE 1). In contrast to related chitinases, MtNFH1 hydrolyzes neither chitin nor chitin fragments, indicating a high cleavage preference for NFs. Here, we provide evidence for a role of MtNFH1 in the symbiosis with Sinorhizobium meliloti...
January 24, 2018: Plant Cell
Xiaomi Wang, Ying Teng, Chen Tu, Yongming Luo, Chris Greening, Ning Zhang, Shixiang Dai, Wenjie Ren, L Zhao, Zhengao Li
Legume-rhizobium symbioses have the potential to remediate soils contaminated with chlorinated organic compounds. Here, the model symbiosis between Medicago sativa and Sinorhizobium meliloti was used to explore the relationships between symbiotic nitrogen fixation and transformation of tetrachlorobiphenyl PCB 77 within this association. 45-day-old seedlings in vermiculite were pre-treated with 5 mg L-1 PCB 77 for 5 days. In PCB-supplemented nodules, addition of the nitrogenase enhancer molybdate significantly stimulated dechlorination by 7...
January 24, 2018: Environmental Science & Technology
Alisa P Lehman, Sharon R Long
Reactive oxygen species such as peroxides play an important role in plant development, cell wall maturation, and defense responses. During nodulation with host plant Medicago sativa, Sinorhizobium meliloti cells are exposed to H2O2 in infection threads and developing nodules (1). S. meliloti likely also experience oxidative stress, from both internal and external sources, during life in the soil. Here, we present microarray transcription data of S. meliloti wild type cells compared to a mutant deficient in the key oxidative regulatory protein OxyR, each in response to H2O2 treatment...
January 22, 2018: Journal of Bacteriology
Marta Robledo, Esther Menéndez, Jose Ignacio Jimenez-Zurdo, Raúl Rivas, Encarna Velazquez, Eustoquio Martinez-Molina, Giles Oldroyd, Pedro F Mateos
The infection of legume plants by rhizobia is tightly regulated to ensure accurate bacterial penetration, infection and development of functionally efficient nitrogen-fixing root nodules. Rhizobial Nod Factors (NF) have key roles in the elicitation of nodulation signalling. Infection of white clover roots also involves the tightly regulated specific breakdown of the non-crystalline apex of cell walls in growing root hairs, which is mediated by Rhizobium leguminosarum bv. trifolii cellulase CelC2. Here, we have analyzed the impact of this endoglucanase on symbiotic signalling in the model legume Medicago truncatula...
January 15, 2018: Molecular Plant-microbe Interactions: MPMI
Erasto Hernández-Calderón, Maria Elizabeth Aviles-Garcia, Diana Yazmín Castulo-Rubio, Lourdes Macías-Rodríguez, Vicente Montejano Ramírez, Gustavo Santoyo, José López-Bucio, Eduardo Valencia-Cantero
Our results show that Sorghum bicolor is able to recognize bacteria through its volatile compounds and differentially respond to beneficial or pathogens via eliciting nutritional or defense adaptive traits. Plants establish beneficial, harmful, or neutral relationships with bacteria. Plant growth promoting rhizobacteria (PGPR) emit volatile compounds (VCs), which may act as molecular cues influencing plant development, nutrition, and/or defense. In this study, we compared the effects of VCs produced by bacteria with different lifestyles, including Arthrobacter agilis UMCV2, Bacillus methylotrophicus M4-96, Sinorhizobium meliloti 1021, the plant pathogen Pseudomonas aeruginosa PAO1, and the commensal rhizobacterium Bacillus sp...
January 12, 2018: Plant Molecular Biology
Jan Kutner, Ivan G Shabalin, Dorota Matelska, Katarzyna Handing, Olga Gasiorowska, Piotr Sroka, Maria W Gorna, Krzysztof Ginalski, Krzysztof Wozniak, Wladek Minor
The D-2-hydroxyacid dehydrogenase (2HADH) family illustrates a complex evolutionary history with multiple lateral gene transfers, gene duplications, and losses. As a result, the exact functional annotation of individual members can be extrapolated to a very limited extent. Here, we revise the previous simplified view on the classification of the 2HADH family; specifically, we show that the previously delineated glyoxylate/hydroxypyruvate reductase (GHPR) subfamily consists of two evolutionary separated GHRA and GHRB subfamilies...
January 8, 2018: Biochemistry
Marta Robledo, Natalia I García-Tomsig, José I Jiménez-Zurdo
High-throughput transcriptome profiling (RNAseq) has uncovered large and heterogeneous populations of small noncoding RNA species (sRNAs) with potential regulatory roles in bacteria. A large fraction of sRNAs are differentially regulated and rely on protein-assisted antisense interactions to trans-encoded target mRNAs to fine-tune posttranscriptional reprogramming of gene expression in response to external cues. However, annotation and function of sRNAs are still largely overlooked in nonmodel bacteria with complex lifestyles...
2018: Methods in Molecular Biology
Masahiro Ito, Masato Morino, Terry A Krulwich
Mrp (Multiple resistance and pH) antiporter was identified as a gene complementing an alkaline-sensitive mutant strain of alkaliphilic Bacillus halodurans C-125 in 1990. At that time, there was no example of a multi-subunit type Na+ /H+ antiporter comprising six or seven hydrophobic proteins, and it was newly designated as the monovalent cation: proton antiporter-3 (CPA3) family in the classification of transporters. The Mrp antiporter is broadly distributed among bacteria and archaea, not only in alkaliphiles...
2017: Frontiers in Microbiology
Germán Ceizel Borella, Antonio Lagares, Claudio Valverde
In the N2-fixing symbiont of alfalfa root nodules, Sinorhizobium meliloti 2011, the mmgR gene encodes a 77 nt small untranslated RNA (sRNA) that negatively regulates the accumulation of polyhydroxybutyrate (PHB) when the bacterium is grown under conditions of surplus carbon (C) in relation to nitrogen (N). We previously showed that the expression of mmgR is primarily controlled at the transcriptional level and that it depends on the cellular N status, although the regulatory mechanism and the factors involved were unknown...
January 2018: Microbiology
Hisayuki Mitsui, Kiwamu Minamisawa
The plant symbiotic α-proteobacterium Sinorhizobium meliloti has two RpoH-type sigma factors, RpoH1 and RpoH2. The former induces the synthesis of heat shock proteins and optimizes interactions with the host. Using a Western blot analysis, we examined time course changes in the intracellular contents of these factors upon a temperature upshift. The RpoH1 level was relatively high and constant, suggesting that its regulatory role in the heat shock response is attained through the activation of the pre-existing RpoH1 protein...
December 27, 2017: Microbes and Environments
Loubna Benidire, Majida Lahrouni, Khalid Daoui, Zain El Abidine Fatemi, Ricardo Gomez Carmona, Michael Göttfert, Khalid Oufdou
Rhizobia are symbiotic nitrogen-fixing bacteria in root nodules of legumes. In Morocco, faba bean (Vicia faba L.), which is the main legume crop cultivated in the country, is often grown in marginal soils of arid and semi-arid regions. This study examines the phenotypic diversity of rhizobia nodulating V. faba isolated from different regions in Morocco for tolerance to some abiotic stresses. A total of 106 rhizobia strains isolated from nodules were identified at the species level by analysing 16S rDNA. Additionally, for selected strains recA, otsA, kup and nodA fragments were sequenced...
January 2018: Systematic and Applied Microbiology
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