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Current Topics in Microbiology and Immunology

Melene A Thompson, Maureen C Onyeziri, Clay Fuqua
Agrobacterium tumefaciens attaches stably to plant host tissues and abiotic surfaces. During pathogenesis, physical attachment to the site of infection is a prerequisite to infection and horizontal gene transfer to the plant. Virulent and avirulent strains may also attach to plant tissue in more benign plant associations, and as with other soil microbes, to soil surfaces in the terrestrial environment. Although most A. tumefaciens virulence functions are encoded on the tumor-inducing plasmid, genes that direct general surface attachment are chromosomally encoded, and thus this process is not obligatorily tied to virulence, but is a more fundamental capacity...
July 12, 2018: Current Topics in Microbiology and Immunology
Chih-Feng Wu, Delaney A Smith, Erh-Min Lai, Jeff H Chang
The bacterial type VI secretion system (T6SS) is a contractile nanomachine dedicated to delivering molecules out of bacterial cells. T6SS-encoding loci are in the genome sequences of many Gram-negative bacteria, and T6SS has been implicated in a plethora of roles. In the majority of cases, the T6SSs deliver effector proteins in a contact-dependent manner to antagonize other bacteria. Current models suggest that the effectors are deployed to influence social interactions in microbial communities. In this chapter, we describe the structure, function, and regulation of the T6SS and its effectors...
July 11, 2018: Current Topics in Microbiology and Immunology
Kamy Singer
The mechanism of T-DNA integration into plant genomes during Agrobacterium-mediated genetic transformation is still not understood. As genetic transformation of plants via Agrobacterium has become a routine practice among plant biologists, understanding T-DNA integration remains important for several reasons. First, T-DNA is the final step in one of the unique cases of inter-kingdom horizontal gene transfer in nature. Second, understanding T-DNA integration is important for biotechnological applications. For example, better knowledge of this process may help develop methods to transform species that are currently not susceptible to Agrobacterium-mediated transformation...
July 11, 2018: Current Topics in Microbiology and Immunology
Ann G Matthysse
Agrobacterium exopolysaccharides play a major role in the life of the cell. Exopolysaccharides are required for bacterial growth as a biofilm and they protect the bacteria against environmental stresses. Five of the exopolysaccharides made by A. tumefaciens have been characterized extensively with respect to their structure, synthesis, regulation, and role in the life of the bacteria. These are cyclic-β-(1, 2)-glucan, cellulose, curdlan, succinoglycan, and the unipolar polysaccharide (UPP). This chapter describes the structure, synthesis, regulation, and function of these five exopolysaccharides...
July 11, 2018: Current Topics in Microbiology and Immunology
Ajith Anand, Todd J Jones
The last decade has seen significant strides in Agrobacterium-mediated plant transformation technology. This has not only expanded the number of crop species that can be transformed by Agrobacterium, but has also made it possible to routinely transform several recalcitrant crop species including cereals (e.g., maize, sorghum, and wheat). However, the technology is limited by the random nature of DNA insertions, genotype dependency, low frequency of quality events, and variation in gene expression arising from genomic insertion sites...
June 30, 2018: Current Topics in Microbiology and Immunology
Richard T Marconi
No abstract text is available yet for this article.
June 28, 2018: Current Topics in Microbiology and Immunology
Charlotte Rodrigues Neves, Susan Gibbs
Contact with the skin is inevitable or desirable for daily life products such as cosmetics, hair dyes, perfumes, drugs, household products, and industrial and agricultural products. Whereas the majority of these products are harmless, a number can become metabolized and/or activate the immunological defense via innate and adaptive mechanisms resulting in sensitization and allergic contact dermatitis upon following exposures to the same substance. Therefore, strict safety (hazard) assessment of actives and ingredients in products and drugs applied to the skin is essential to determine I) whether the chemical is a potential sensitizer and if so II) what is the safe concentration for human exposure to prevent sensitization from occurring...
June 23, 2018: Current Topics in Microbiology and Immunology
Yang Grace Li, Peter J Christie
The Agrobacterium tumefaciens VirB/VirD4 translocation machine is a member of a superfamily of translocators designated as type IV secretion systems (T4SSs) that function in many species of gram-negative and gram-positive bacteria. T4SSs evolved from ancestral conjugation systems for specialized purposes relating to bacterial colonization or infection. A. tumefaciens employs the VirB/VirD4 T4SS to deliver oncogenic DNA (T-DNA) and effector proteins to plant cells, causing the tumorous disease called crown gall...
May 29, 2018: Current Topics in Microbiology and Immunology
Mattias Svensson, Puran Chen
Biomedical research aiming to understand the molecular basis of human lung tissue development, homeostasis and disease, or to develop new therapies for human respiratory diseases, requires models that faithfully recapitulate the human condition. This has stimulated biologists and engineers to develop in vitro organotypic models mimicking human respiratory tissues. In this chapter, we provide examples of different types of model systems ranging from simple unicellular cultures to more complex multicellular systems...
May 29, 2018: Current Topics in Microbiology and Immunology
Wanda M Figueroa-Cuilan, Pamela J B Brown
A great diversity of bacterial cell shapes can be found in nature, suggesting that cell wall biogenesis is regulated both spatially and temporally. Although Agrobacterium tumefaciens has a rod-shaped morphology, the mechanisms underlying cell growth are strikingly different than other well-studied rod-shaped bacteria including Escherichia coli. Technological advances, such as the ability to deplete essential genes and the development of fluorescent D-amino acids, have enabled recent advances in our understanding of cell wall biogenesis during cell elongation and division of A...
May 29, 2018: Current Topics in Microbiology and Immunology
Léon Otten
The transfer of T-DNA sequences from Agrobacterium to plant cells is a well-understood process of natural genetic engineering. The expression of T-DNA genes in plants leads to tumors, hairy roots, or transgenic plants. The transformed cells multiply and synthesize small molecules, called opines, used by Agrobacteria for their growth. Several T-DNA genes stimulate or influence plant growth. Among these, iaaH and iaaM encode proteins involved in auxin synthesis, whereas ipt encodes a protein involved in cytokinin synthesis...
May 17, 2018: Current Topics in Microbiology and Immunology
Paul J J Hooykaas, G Paul H van Heusden, Xiaolei Niu, M Reza Roushan, Jalal Soltani, Xiaorong Zhang, Bert J van der Zaal
Two decades ago, it was discovered that the well-known plant vector Agrobacterium tumefaciens can also transform yeasts and fungi when these microorganisms are co-cultivated on a solid substrate in the presence of a phenolic inducer such as acetosyringone. It is important that the medium has a low pH (5-6) and that the temperature is kept at room temperature (20-25 °C) during co-cultivation. Nowadays, Agrobacterium-mediated transformation (AMT) is the method of choice for the transformation of many fungal species; as the method is simple, the transformation efficiencies are much higher than with other methods, and AMT leads to single-copy integration much more frequently than do other methods...
May 17, 2018: Current Topics in Microbiology and Immunology
Lucio Gama, Celina Abreu, Erin N Shirk, Suzanne E Queen, Sarah E Beck, Kelly A Metcalf Pate, Brandon T Bullock, M Christine Zink, Joseph L Mankowski, Janice E Clements
Lentiviruses infect myeloid cells, leading to acute infection followed by persistent/latent infections not cleared by the host immune system. HIV and SIV are lentiviruses that infect CD4+ lymphocytes in addition to myeloid cells in blood and tissues. HIV infection of myeloid cells in brain, lung, and heart causes tissue-specific diseases that are mostly observed during severe immunosuppression, when the number of circulating CD4+ T cells declines to exceeding low levels. Antiretroviral therapy (ART) controls viral replication but does not successfully eliminate latent virus, which leads to viral rebound once ART is interrupted...
May 17, 2018: Current Topics in Microbiology and Immunology
Dieter Bulach, Ben Adler
Until about 15 years ago, the molecular and cellular basis for pathogenesis in leptospirosis was virtually unknown. The determination of the first full genome sequence in 2003 was followed rapidly by other whole genome sequences, whose availability facilitated the development of transposon mutagenesis and then directed mutagenesis of pathogenic Leptospira spp. The combination of genomics, transcriptomics and mutant construction and characterisation has resulted in major progress in our understanding of the taxonomy and biology of Leptospira...
April 26, 2018: Current Topics in Microbiology and Immunology
Y Dessaux, D Faure
Agrobacterium populations live in different habitats (bare soil, rhizosphere, host plants), and hence face different environmental constraints. They have evolved the capacity to exploit diverse resources and to escape plant defense and competition from other microbiota. By modifying the genome of their host, Agrobacterium populations exhibit the remarkable ability to construct and exploit the ecological niche of the plant tumors that they incite. This niche is characterized by the accumulation of specific, low molecular weight compounds termed opines that play a critical role in Agrobacterium 's lifestyle...
March 20, 2018: Current Topics in Microbiology and Immunology
Pilar Carranza-Rosales, Nancy Elena Guzmán-Delgado, Irma Edith Carranza-Torres, Ezequiel Viveros-Valdez, Javier Morán-Martínez
Breast cancer is the most common cancer type diagnosed in women, it represents a critical public health problem worldwide, with 1,671,149 estimated new cases and nearly 571,000 related deaths. Research on breast cancer has mainly been conducted using two-dimensional (2D) cell cultures and animal models. The usefulness of these models is reflected in the vast knowledge accumulated over the past decades. However, considering that animal models are three-dimensional (3D) in nature, the validity of the studies using 2D cell cultures has recently been questioned...
March 20, 2018: Current Topics in Microbiology and Immunology
Nemanja Kuzmanović, Joanna Puławska, Lingyun Hao, Thomas J Burr
Agrobacterium vitis is the primary causal agent of grapevine crown gall worldwide. Symptoms of grapevine crown gall disease include tumor formation on the aerial plant parts, whereas both tumorigenic and nontumorigenic strains of A. vitis cause root necrosis. Genetic and genomic analyses indicated that A. vitis is distinguishable from the members of the Agrobacterium genus and its transfer to the genus Allorhizobium was suggested. A. vitis is genetically diverse, with respect to both chromosomal and plasmid DNA...
March 20, 2018: Current Topics in Microbiology and Immunology
Keunsub Lee, Kan Wang
During the last decade, small noncoding RNAs (ncRNAs) have emerged as essential post-transcriptional regulators in bacteria. Nearly all important physiological and stress responses are modulated by ncRNA regulators, such as riboswitches, trans-acting small RNAs (sRNAs), and cis-antisense RNAs. Recently, three RNA-seq studies identified a total of 1534 candidate ncRNAs from Agrobacterium tumefaciens, a pathogen and biotechnology tool for plants. Only a few ncRNAs have been functionally characterized in A. tumefaciens, and some of them appear to be involved in virulence...
March 20, 2018: Current Topics in Microbiology and Immunology
Han Ming Gan, Michael A Savka
This chapter presents a historical overview of the development and changes in scientific approaches to classifying members of the Agrobacterium genus. We also describe the changes in the inference of evolutionary relationships among Agrobacterium biovars and Agrobacterium strains from using the 16S rRNA marker to recA genes and to the use of multilocus sequence analysis (MLSA). Further, the impacts of the genomic era enabling low cost and rapid whole genome sequencing on Agrobacterium phylogeny are reviewed with a focus on the use of new and sophisticated bioinformatics approaches to refine phylogenetic inferences...
March 3, 2018: Current Topics in Microbiology and Immunology
Benoît Lacroix, Vitaly Citovsky
Besides the massive gene transfer from organelles to the nuclear genomes, which occurred during the early evolution of eukaryote lineages, the importance of horizontal gene transfer (HGT) in eukaryotes remains controversial. Yet, increasing amounts of genomic data reveal many cases of bacterium-to-eukaryote HGT that likely represent a significant force in adaptive evolution of eukaryotic species. However, DNA transfer involved in genetic transformation of plants by Agrobacterium species has traditionally been considered as the unique example of natural DNA transfer and integration into eukaryotic genomes...
March 3, 2018: Current Topics in Microbiology and Immunology
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