Complete Genome Sequence of Agrobacterium tumefaciens 1D1609

ABSTRACT Agrobacterium tumefaciens 1D1609 is a highly virulent strain isolated from a crown gall tumor of alfalfa (Medicago sativa L.). Compared to other well-characterized A. tumefaciens strains, such as C58 and Ach5, 1D1609 has a distinctive host range. Here, we report its complete genome sequence to facilitate future studies.

Two Agrobacterium tumefaciens CheW Proteins Are Incorporated into One Chemosensory Pathway with Different Efficiencies

Agrobacterium tumefaciens is the agent that causes crown gall tumor disease on more than 140 species of dicotyledonous plants. Chemotaxis of A. tumefaciens toward the wound sites of the host plant is the first step to recognize the host. CheW is a coupling protein that bridges the histidine kinase CheA and the chemoreceptors to form the chemotaxis core signaling complex and plays a crucial role in the assembly and function of the large chemosensory array. Unlike all previously reported chemotaxis systems, A. tumefaciens has only one major che operon but two cheW homologs (atu2075 as cheW1 and atu2617 as cheW2) on unlinked loci. The in-frame deletion of either cheW gene significantly affects A. tumefaciens chemotaxis but does not abolish the chemotaxis, unless both cheW genes were deleted. The effect of cheW2 deletion on the chemotaxis is more severe than that of cheW1 deletion. Either CheW can interact with CheA and couple it to the cell poles. The promoter activity of cheW2 is always higher than that of cheW1 under all of the tested conditions. When two cheW genes were adjusted to the same expression level by using the identical promoter, the difference between the effects of two CheW proteins on the chemotaxis still existed. Therefore, we envision that both the different molecular ratio of two CheW proteins in cell and the different affinities of two CheW proteins with CheA and chemoreceptors result in the efficiency difference of two CheW proteins in functioning in the large chemosensory array.

ROLE OF SUSPENDED PARTICULATE MATTER IN ANGIOGENESIS EMPLOYING CROWN GALL TUMOR ASSAY

<p><strong>Objective: </strong>Aim of the study was to screen the suspended particulate matter for their role in enhancing angiogenesis employing crown gall tumor assay.</p><p><strong>Methods: </strong>Particulate matter (PM₁₀) samples were collected, on glass fiber filter paper at the rate of 1.12–1.14 m^3/min for 8 hr using high volume sampler, from six different sites of Amritsar city. Aqueous extracts of suspended particulate matter were prepared using a mechanical shaker for 24 hour and the filtrate was centrifuged and lyophilized.</p><p><strong>Results: </strong>Maximum (34.67±1.764) tumors were induced by samples collected from Crystal chowk whereas tumor inducing ratio (TIR) was found to be comparably high for two sites <em>viz.,</em> Crystal chowk and Bhandari bridge.</p><p><strong>Conclusion: </strong>High tumor inducing ratio at the above-mentioned sites was correlated to high traffic emission from automobile exhaust. Crown gall tumor assay has been proved to be rapid, economical and reliable screening assay for angiogenesis agent.</p>

Grapevine (Vitis vinifera) Crown Galls Host Distinct Microbiota

ABSTRACTCrown gall disease of grapevine is caused by virulentAgrobacteriumstrains and establishes a suitable habitat for agrobacteria and, potentially, other bacteria. The microbial community associated with grapevine plants has not been investigated with respect to this disease, which frequently results in monetary losses. This study compares the endophytic microbiota of organs from grapevine plants with or without crown gall disease and the surrounding vineyard soil over the growing seasons of 1 year. Amplicon-based community profiling revealed that the dominating factor causing differences between the grapevine microbiota is the sample site, not the crown gall disease. The soil showed the highest microbial diversity, which decreased with the distance from the soil over the root and the graft union of the trunk to the cane. Only the graft union microbiota was significantly affected by crown gall disease. The bacterial community of graft unions without a crown gall hosted transient microbiota, with the three most abundant bacterial species changing from season to season. In contrast, graft unions with a crown gall had a higher species richness, which in every season was dominated by the same three bacteria (Pseudomonassp.,Enterobacteriaceaesp., andAgrobacterium vitis). Forin vitro-cultivated grapevine plantlets,A. vitisinfection alone was sufficient to cause crown gall disease. Our data show that microbiota in crown galls is more stable over time than microbiota in healthy graft unions and that the microbial community is not essential for crown gall disease outbreak.IMPORTANCEThe characterization of bacterial populations in animal and human diseases using high-throughput deep-sequencing technologies, such as 16S amplicon sequencing, will ideally result in the identification of disease-specific microbiota. We analyzed the microbiota of the crown gall disease of grapevine, which is caused by infection with the bacterial pathogenAgrobacterium vitis.All otherAgrobacteriumspecies were found to be avirulent, even though they lived together withA. vitisin the same crown gall tumor. As has been reported for human cancer, the crown gall tumor also hosted opportunistic bacteria that are adapted to the tumor microenvironment. Characterization of the microbiota in various diseases using amplicon sequencing may help in early diagnosis, to serve as a preventative measure of disease in the future.