scholarly journals The Novel Genes emmABC Are Associated with Exopolysaccharide Production, Motility, Stress Adaptation, and Symbiosis in Sinorhizobium meliloti

2009 ◽  
Vol 191 (19) ◽  
pp. 5890-5900 ◽  
Author(s):  
Jennifer Morris ◽  
Juan E. González
Keyword(s):  
Sinorhizobium Meliloti ◽  
Genetic Factors ◽  
Leguminous Plant ◽  
The Novel ◽  
Two Component System ◽  
Cell Component ◽  
Plant Host ◽  
Free Living ◽  
Novel Genes ◽  
Exopolysaccharide Production

ABSTRACT The nitrogen-fixing symbiont Sinorhizobium meliloti senses and responds to constantly changing environmental conditions as it makes its way through the soil in search of its leguminous plant host, Medicago sativa (alfalfa). As a result, this bacterium regulates various aspects of its physiology in order to respond appropriately to stress, starvation, and competition. For example, exopolysaccharide production, which has been shown to play an important role in the ability of S. meliloti to successfully invade its host, also helps the bacterium withstand osmotic changes and other environmental stresses. In an effort to further elucidate the intricate regulation of this important cell component, we set out to identify genetic factors that may affect its production. Here we characterize novel genes that encode a small protein (EmmA) and a putative two-component system (EmmB-EmmC). A mutation in any of these genes leads to increased production of the symbiotically important exopolysaccharide succinoglycan. In addition, emm mutants display membrane-associated defects, are nonmotile, and are unable to form an optimal symbiosis with alfalfa, suggesting that these novel genes may play a greater role in the overall fitness of S. meliloti both during the free-living stage and in its association with its host.

scholarly journals Sinorhizobium meliloti SyrA Mediates the Transcriptional Regulation of Genes Involved in Lipopolysaccharide Sulfation and Exopolysaccharide Biosynthesis

2007 ◽  
Vol 189 (6) ◽  
pp. 2510-2520 ◽  
Author(s):  
David H. Keating
Keyword(s):  
Sinorhizobium Meliloti ◽  
Response Regulator ◽  
Living Conditions ◽  
Wild Type ◽  
Two Component System ◽  
Free Living ◽  
Component System ◽  
Two Component ◽  
Exopolysaccharide Biosynthesis ◽  
Free Living Conditions

ABSTRACT Sinorhizobium meliloti is a gram-negative soil bacterium found either in free-living form or as a nitrogen-fixing endosymbiont of leguminous plants such as Medicago sativa (alfalfa). S. meliloti synthesizes an unusual sulfate-modified form of lipopolysaccharide (LPS). A recent study reported the identification of a gene, lpsS, which encodes an LPS sulfotransferase activity in S. meliloti. Mutants bearing a disrupted version of lpsS exhibit an altered symbiosis, in that they elicit more nodules than wild type. However, under free-living conditions, the lpsS mutant displayed no change in LPS sulfation. These data suggest that the expression of lpsS is differentially regulated, such that it is transcriptionally repressed during free-living conditions but upregulated during symbiosis. Here, I show that the expression of lpsS is upregulated in strains that constitutively express the symbiotic regulator SyrA. SyrA is a small protein that lacks an apparent DNA binding domain and is predicted to be located in the cytoplasmic membrane yet is sufficient to upregulate lpsS transcription. Furthermore, SyrA can mediate the transcriptional upregulation of exo genes involved in the biosynthesis of the symbiotic exopolysaccharide succinoglycan. The SyrA-mediated transcriptional upregulation of lpsS and exo transcription is blocked in mutants harboring a mutation in chvI, which encodes the response regulator of a conserved two-component system. Thus, SyrA likely acts indirectly to promote transcriptional upregulation of lpsS and exo genes through a mechanism that requires the ExoS/ChvI two-component system.

scholarly journals Autoregulation of Sinorhizobium meliloti exoR gene expression

Microbiology ◽  
2010 ◽  
Vol 156 (7) ◽  
pp. 2092-2101 ◽  
Author(s):  
Hai-Yang Lu ◽  
Hai-Ping Cheng
Keyword(s):  
Sinorhizobium Meliloti ◽  
Carbon Sources ◽  
Regulatory System ◽  
Leguminous Plant ◽  
Wild Type ◽  
Plant Host ◽  
Active Sensor ◽  
Bacterial Exopolysaccharide ◽  
Membrane Bound ◽  
And Control

The successful nitrogen-fixing symbiosis between the Gram-negative soil bacterium Sinorhizobium meliloti and its leguminous plant host alfalfa (Medicago sativa) requires the bacterial exopolysaccharide succinoglycan. Succinoglycan and flagellum production, along with the ability to metabolize more than 20 different carbon sources and control the expression of a large number of S. meliloti genes, is regulated by the ExoR–ExoS/ChvI signalling pathway. The ExoR protein interacts with and suppresses the sensing activities of ExoS, the membrane-bound sensor of the ExoS/ChvI two-component regulatory system. Here we show that exoR expression is clearly upregulated in the absence of any functional ExoR protein. This upregulation was suppressed by the presence of the wild-type ExoR protein but not by a mutated ExoR protein lacking signal peptide. The levels of exoR expression could be directly modified in real time by changing the levels of total ExoR protein. The expression of exoR was also upregulated by the constitutively active sensor mutation exoS96, and blocked by two single mutations, exoS* and exoSsupA , in the ExoS sensing domain. Presence of the wild-type ExoS protein further elevated the levels of exoR expression in the absence of functional ExoR protein, and reversed the effects of exoS96, exoS* and exoSsupA mutations. Altogether, these data suggest that ExoR protein autoregulates exoR expression through the ExoS/ChvI system, allowing S. meliloti cells to maintain the levels of exoR expression based on the amount of total ExoR protein.

The two-component system ActJK is involved in acid stress tolerance and symbiosis in Sinorhizobium meliloti

2021 ◽  
Vol 329 ◽  
pp. 80-91
Author(s):  
Francisco J. Albicoro ◽  
Walter O. Draghi ◽  
María C. Martini ◽  
María E. Salas ◽  
G.A. Torres Tejerizo ◽  
...  
Keyword(s):  
Stress Tolerance ◽  
Sinorhizobium Meliloti ◽  
Acid Stress ◽  
Two Component System ◽  
Component System ◽  
Two Component

scholarly journals Paraburkholderia phymatum Homocitrate Synthase NifV Plays a Key Role for Nitrogenase Activity during Symbiosis with Papilionoids and in Free-Living Growth Conditions

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 952
Author(s):  
Paula Bellés-Sancho ◽  
Martina Lardi ◽  
Yilei Liu ◽  
Sebastian Hug ◽  
Marta Adriana Pinto-Carbó ◽  
...  
Keyword(s):  
Nitrogenase Activity ◽  
Root Nodules ◽  
Growth Conditions ◽  
Lysine Biosynthesis ◽  
Metabolome Analysis ◽  
Plant Host ◽  
Free Living ◽  
Bacterial Enzyme ◽  
Homocitrate Synthase ◽  
Iron Molybdenum Cofactor

Homocitrate is an essential component of the iron-molybdenum cofactor of nitrogenase, the bacterial enzyme that catalyzes the reduction of dinitrogen (N2) to ammonia. In nitrogen-fixing and nodulating alpha-rhizobia, homocitrate is usually provided to bacteroids in root nodules by their plant host. In contrast, non-nodulating free-living diazotrophs encode the homocitrate synthase (NifV) and reduce N2 in nitrogen-limiting free-living conditions. Paraburkholderia phymatum STM815 is a beta-rhizobial strain, which can enter symbiosis with a broad range of legumes, including papilionoids and mimosoids. In contrast to most alpha-rhizobia, which lack nifV, P. phymatum harbors a copy of nifV on its symbiotic plasmid. We show here that P. phymatum nifV is essential for nitrogenase activity both in root nodules of papilionoid plants and in free-living growth conditions. Notably, nifV was dispensable in nodules of Mimosa pudica despite the fact that the gene was highly expressed during symbiosis with all tested papilionoid and mimosoid plants. A metabolome analysis of papilionoid and mimosoid root nodules infected with the P. phymatum wild-type strain revealed that among the approximately 400 measured metabolites, homocitrate and other metabolites involved in lysine biosynthesis and degradation have accumulated in all plant nodules compared to uninfected roots, suggesting an important role of these metabolites during symbiosis.

scholarly journals Cyclic Di-GMP Regulates Multiple Cellular Functions in the Symbiotic Alphaproteobacterium Sinorhizobium meliloti

2015 ◽  
Vol 198 (3) ◽  
pp. 521-535 ◽  
Author(s):  
Simon Schäper ◽  
Elizaveta Krol ◽  
Dorota Skotnicka ◽  
Volkhard Kaever ◽  
Rolf Hilker ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Sinorhizobium Meliloti ◽  
Acid Stress ◽  
Second Messenger ◽  
Lifestyle Changes ◽  
Single Domain ◽  
Receptor Protein ◽  
Leguminous Plant ◽  
Content Type

ABSTRACTSinorhizobium melilotiundergoes major lifestyle changes between planktonic states, biofilm formation, and symbiosis with leguminous plant hosts. In many bacteria, the second messenger 3′,5′-cyclic di-GMP (c-di-GMP, or cdG) promotes a sessile lifestyle by regulating a plethora of processes involved in biofilm formation, including motility and biosynthesis of exopolysaccharides (EPS). Here, we systematically investigated the role of cdG inS. melilotiRm2011 encoding 22 proteins putatively associated with cdG synthesis, degradation, or binding. Single mutations in 21 of these genes did not cause evident changes in biofilm formation, motility, or EPS biosynthesis. In contrast, manipulation of cdG levels by overproducing endogenous or heterologous diguanylate cyclases (DGCs) or phosphodiesterases (PDEs) affected these processes and accumulation ofN-Acyl-homoserine lactones in the culture supernatant. Specifically, individual overexpression of theS. melilotigenespleD,SMb20523,SMb20447,SMc01464, andSMc03178encoding putative DGCs and ofSMb21517encoding a single-domain PDE protein had an impact and resulted in increased levels of cdG. Compared to the wild type, anS. melilotistrain that did not produce detectable levels of cdG (cdG0) was more sensitive to acid stress. However, it was symbiotically potent, unaffected in motility, and only slightly reduced in biofilm formation. TheSMc01790-SMc01796locus, homologous to theAgrobacterium tumefaciensuppABCDEFcluster governing biosynthesis of a unipolarly localized polysaccharide, was found to be required for cdG-stimulated biofilm formation, while the single-domain PilZ protein McrA was identified as a cdG receptor protein involved in regulation of motility.IMPORTANCEWe present the first systematic genome-wide investigation of the role of 3′,5′-cyclic di-GMP (c-di-GMP, or cdG) in regulation of motility, biosynthesis of exopolysaccharides, biofilm formation, quorum sensing, and symbiosis in a symbiotic alpha-rhizobial species. Phenotypes of anS. melilotistrain unable to produce cdG (cdG0) demonstrated that this second messenger is not essential for root nodule symbiosis but may contribute to acid tolerance. Our data further suggest that enhanced levels of cdG promote sessility ofS. melilotiand uncovered a single-domain PilZ protein as regulator of motility.

Cerebrovascular complications of novel coronavirus infection in young and middle-aged people

2021 ◽  
pp. 21-25
Author(s):  
F. Z. Olimova ◽  
Ye. G. Klocheva ◽  
S. V. Lobzin ◽  
V. V. Goldobin ◽  
M. S. Partavi
Keyword(s):  
Blood Coagulation ◽  
Genetic Factors ◽  
Cerebrovascular Disorders ◽  
Coagulation System ◽  
The Novel ◽  
Middle Aged ◽  
Aged People ◽  
Cerebrovascular Complications ◽  
Coronavirus Infection ◽  
Novel Coronavirus

The novel coronavirus (SARS‑CoV‑2) infection manifested by a pandemic and has a wide range of complications, including the nervous system’s complications. Despite the fact that older people with comorbidities are more at risk of developing complications from the sequelae of previous COVID‑19 disease, a significant link between the novel coronavirus infection and cerebrovascular disorders in young and middle‑aged people is increasingly mentioned in the literature. The development of cerebrovascular complications in these people not only depends on the damaging effect of the novel coronavirus infection on the macroorganism, but also on a number of other factors, in particular, on the genetic factors of the blood coagulation system. Further study of the possible influence the novel coronavirus infection on the development of cerebrovascular complications, taking into account the genetic factors of the blood coagulation system in young and middle‑aged people will provide early prevention and timely correction of cerebrovascular disorders.

scholarly journals Genomic Insights Into the Lifestyles of Thaumarchaeota Inside Sponges

2021 ◽  
Vol 11 ◽  
Author(s):  
Markus Haber ◽  
Ilia Burgsdorf ◽  
Kim M. Handley ◽  
Maxim Rubin-Blum ◽  
Laura Steindler
Keyword(s):  
The Novel ◽  
Glycine Cleavage System ◽  
Free Living ◽  
High Affinity ◽  
Branched Chain Amino Acid ◽  
Glycine Cleavage ◽  
Microbial Symbionts ◽  
Host Sponge ◽  
Branched Chain ◽  
Sponge Symbionts

Sponges are among the oldest metazoans and their success is partly due to their abundant and diverse microbial symbionts. They are one of the few animals that have Thaumarchaeota symbionts. Here we compare genomes of 11 Thaumarchaeota sponge symbionts, including three new genomes, to free-living ones. Like their free-living counterparts, sponge-associated Thaumarchaeota can oxidize ammonia, fix carbon, and produce several vitamins. Adaptions to life inside the sponge host include enrichment in transposases, toxin-antitoxin systems and restriction modifications systems, enrichments previously reported also from bacterial sponge symbionts. Most thaumarchaeal sponge symbionts lost the ability to synthesize rhamnose, which likely alters their cell surface and allows them to evade digestion by the host. All but one archaeal sponge symbiont encoded a high-affinity, branched-chain amino acid transporter system that was absent from the analyzed free-living thaumarchaeota suggesting a mixotrophic lifestyle for the sponge symbionts. Most of the other unique features found in sponge-associated Thaumarchaeota, were limited to only a few specific symbionts. These features included the presence of exopolyphosphatases and a glycine cleavage system found in the novel genomes. Thaumarchaeota have thus likely highly specific interactions with their sponge host, which is supported by the limited number of host sponge species to which each of these symbionts is restricted.

Polyamine biosynthesis and biological roles in rhizobia

2019 ◽  
Vol 366 (7) ◽  
Author(s):  
Victor A Becerra-Rivera ◽  
Michael F Dunn
Keyword(s):  
Stress Resistance ◽  
Biofilm Formation ◽  
Sinorhizobium Meliloti ◽  
Growth Stress ◽  
Nitrogen Fixing ◽  
Amino Groups ◽  
Nitrogen Fixing Bacteria ◽  
Polyamine Biosynthesis ◽  
Exopolysaccharide Production

ABSTRACTPolyamines are ubiquitous molecules containing two or more amino groups that fulfill varied and often essential physiological and regulatory roles in all organisms. In the symbiotic nitrogen-fixing bacteria known as rhizobia, putrescine and homospermidine are invariably produced while spermidine and norspermidine synthesis appears to be restricted to the alfalfa microsymbiont Sinorhizobium meliloti. Studies with rhizobial mutants deficient in the synthesis of one or more polyamines have shown that these compounds are important for growth, stress resistance, motility, exopolysaccharide production and biofilm formation. In this review, we describe these studies and examine how polyamines are synthesized and regulated in rhizobia.

scholarly journals Comparative Genomics of Myxobacterial Chemosensory Systems

2017 ◽  
Vol 200 (3) ◽  
Author(s):  
Gaurav Sharma ◽  
Indu Khatri ◽  
Srikrishna Subramanian
Keyword(s):  
Myxococcus Xanthus ◽  
Modular Organization ◽  
The Novel ◽  
Single System ◽  
Two Component System ◽  
Content Type ◽  
Chemical Gradients ◽  
Evolutionary Relatedness ◽  
Chemosensory Systems ◽  
Comprehensive Study

ABSTRACTChemosensory systems (CSS) are among the most complex organizations of proteins functioning cooperatively to regulate bacterial motility and other cellular activities. These systems have been studied extensively in bacteria, and usually, they are present as a single system. Eight CSS, the highest number in bacteria, have been reported inMyxococcus xanthusDK1622 and are involved in coordinating diverse functions. Here, we have explored and compared the CSS in all available genomes of orderMyxococcales. Myxococcalesmembers contain 97 to 476 two-component system (TCS) proteins, which assist the bacteria in surviving and adapting to varying environmental conditions. The number of myxobacterial CSS ranges between 1 and 12, with the largest number in familyCystobacteraceaeand the smallest inNannocystaceae. CheA protein was used as a phylogenetic marker to infer evolutionary relatedness between different CSS, and six novel CSS (“extra CSS” [ECSS]) were thus identified in the myxobacteria besides the previously reported Che1 to Che8 systems fromM. xanthus. Che1 to Che8 systems are monophyletic to deltaproteobacteria, whereas the newly identified ECSS form separate clades with different bacterial classes. The comparative modular organization was concordant with the phylogeny. Four clusters lacking CheA proteins were also identified via CheB-based phylogenetic analysis and were categorized as accessory CSS (ACSS). InArchangium, an orphan CSS was identified, in which both CheA and CheB were absent. The novel, accessory, and orphan multimodular CSS identified here suggest the emergence of myxobacterial CSS and could assist in further characterizing their roles.IMPORTANCEThis study is focused on chemosensory systems (CSS), which help the bacterium in directing its movement toward or away from chemical gradients. CSS are present as a single system in most of the bacteria except in some groups, includingMyxococcus xanthus, which has 8 CSS, the highest number reported to date. This is the first comprehensive study carrying out a comparative analysis of the 22 available myxobacterial genomes, which suggests the evolutionary diversity of these systems. We are interested in understanding the distribution of CSS within all known myxobacteria and their probable evolution.

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