Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.
Pseudomonas is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able to colonize a wide range of niches. Their ease of culture in vitro and availability of an increasing number of Pseudomonas strain genome sequences has made the genus an excellent focus for scientific research; the best studied species include P. aeruginosa in its role as an opportunistic human pathogen, the plant pathogen P. syringae, the soil bacterium P. putida, and the plant growth-promoting P. fluorescens, P. lini, P. migulae, and P. graminis.
Citrus canker is a disease affecting Citrus species caused by the bacterium Xanthomonas. Infection causes lesions on the leaves, stems, and fruit of citrus trees, including lime, oranges, and grapefruit. While not harmful to humans, canker significantly affects the vitality of citrus trees, causing leaves and fruit to drop prematurely; a fruit infected with canker is safe to eat, but too unsightly to be sold.
Bacillus amyloliquefaciens is a species of bacterium in the genus Bacillus that is the source of the BamHI restriction enzyme. It also synthesizes a natural antibiotic protein barnase, a widely studied ribonuclease that forms a famously tight complex with its intracellular inhibitor barstar, and plantazolicin, an antibiotic with selective activity against Bacillus anthracis.
Cupriavidus necator is a Gram-negative soil bacterium of the class Betaproteobacteria.
Ralstonia is a genus of bacteria, previously included in the genus Pseudomonas. It is named after the American bacteriologist Ericka Ralston. Ericka Ralston was born Ericka Barrett in 1944 in Saratoga, California, and died in 2015 in Sebastopol, California. While in graduate school at the University of California at Berkeley, she identified 20 strains of Pseudomonas which formed a phenotypical homologous group, and named them Pseudomonas pickettii, after M.J. Pickett in the Department of Bacteriology at the University of California at Los Angeles, from whom she had received the strains. Later, P. pickettii was transferred to the new genus Ralstonia, along with several other species. She continued her research into bacterial pathogenesis under the name of Ericka Barrett while a professor of microbiology at the University of California at Davis from 1977 until her retirement in 1996.
Ralstonia solanacearum is an aerobic non-spore-forming, Gram-negative, plant pathogenic bacterium. R. solanacearum is soil-borne and motile with a polar flagellar tuft. It colonises the xylem, causing bacterial wilt in a very wide range of potential host plants. It is known as Granville wilt when it occurs in tobacco. Bacterial wilts of tomato, pepper, eggplant, and Irish potato caused by R. solanacearum were among the first diseases that Erwin Frink Smith proved to be caused by a bacterial pathogen. Because of its devastating lethality, R. solanacearum is now one of the more intensively studied phytopathogenic bacteria, and bacterial wilt of tomato is a model system for investigating mechanisms of pathogenesis. Ralstonia was until recently classified as Pseudomonas, with similarity in most aspects, except that it does not produce fluorescent pigment like Pseudomonas. The genomes from different strains vary from 5.5 Mb up to 6 Mb, roughly being 3.5 Mb of a chromosome and 2 Mb of a megaplasmid. While the strain GMI1000 was one of the first phytopathogenic bacteria to have its genome completed, the strain UY031 was the first R. solanacearum to have its methylome reported. Within the R. solanacearum species complex, the four major monophyletic clusters of strains are termed phylotypes, that are geographically distinct: phylotypes I-IV are found in Asia, the Americas, Africa, and Oceania, respectively.
Xanthomonas is a genus of bacteria, many of which cause plant diseases. There are at least 27 plant associated Xanthomonas spp., that all together infect at least 400 plant species. Different species typically have specific host and/or tissue range and colonization strategies.
Ralstonia pickettii is a Gram-negative, rod-shaped, soil bacterium.
Clavibacter michiganensis is an aerobic non-sporulating Gram-positive plant pathogenic actinomycete of the genus Clavibacter. Clavibacter michiganensis has several subspecies. Clavibacter michiganensis subsp. michiganensis causes substantial economic losses worldwide by damaging tomatoes and potatoes.
Curtobacterium flaccumfaciens is a Gram-positive bacterium that causes disease on a variety of plants. Gram-positive bacteria characteristics include small irregular rods, lateral flagella, the ability to persist in aerobic environments, and cells containing catalase. In the interest of studying pathogenicity in plants, the species Curtobacterium flaccumfaciens is broken down further into pathovars, which help to better describe the pathogen.
Orientia tsutsugamushi is a mite-borne bacterium belonging to the family Rickettsiaceae and is responsible for a disease called scrub typhus in humans. It is a natural and an obligate intracellular parasite of mites belonging to the family Trombiculidae. With a genome of only 2.0–2.7 Mb, it has the most repeated DNA sequences among bacterial genomes sequenced so far. The disease, scrub typhus, occurs when infected mite larvae accidentally bite humans. Primarily indicated by undifferentiated febrile illnesses, the infection can be complicated and often fatal.
Bacterial wilt is a complex of diseases that occur in plants such as Cucurbitaceae and Solanaceae and are caused by the pathogens Erwinia tracheiphila, a gram-negative bacterium, or Curtobacterium flaccumfaciens pv. flaccumfaciens, a gram-positive bacterium. Cucumber and muskmelon plants are most susceptible, but squash, pumpkins, and gourds may also become infected.
Cupriavidus metallidurans is a non-spore-forming, Gram-negative bacterium which is adapted to survive several forms of heavy metal stress.
The genus Massilia belongs to the family Oxalobacteriaceae, and describes a group of gram-negative, motile, rod-shaped cells. They may contain either peritrichous or polar flagella. This genus was first described in 1998, after the type species, Massilia timonae, was isolated from the blood of an immunocompromised patient. The genus was named after the old Greek and Roman name for the city of Marseille, France, where the organism was first isolated. The Massilia genus is a diverse group that resides in many different environments, has many heterotrophic means of gathering energy, and is commonly found in association with plants.
TALeffectors are proteins secreted by some β- and γ-proteobacteria. Most of these are Xanthomonads. Plant pathogenic Xanthomonas bacteria are especially known for TALEs, produced via their type III secretion system. These proteins can bind promoter sequences in the host plant and activate the expression of plant genes that aid bacterial infection. The TALE domain responsible for binding to DNA is known to have 1.5 to 33.5 short sequences that are repeated multiple times. Each of these repeats was found to be specific for a certain base pair of the DNA. These repeats also have repeat variable residues (RVD) that can detect specific DNA base pairs. They recognize plant DNA sequences through a central repeat domain consisting of a variable number of ~34 amino acid repeats. There appears to be a one-to-one correspondence between the identity of two critical amino acids in each repeat and each DNA base in the target sequence. These proteins are interesting to researchers both for their role in disease of important crop species and the relative ease of retargeting them to bind new DNA sequences. Similar proteins can be found in the pathogenic bacterium Ralstonia solanacearum and Burkholderia rhizoxinica, as well as yet unidentified marine microorganisms. The term TALE-likes is used to refer to the putative protein family encompassing the TALEs and these related proteins.
Liberibacter is a genus of Gram-negative bacteria in the Rhizobiaceae family. Detection of the liberibacteria is based on PCR amplification of their 16S rRNA gene with specific primers. Members of the genus are plant pathogens mostly transmitted by psyllids. The genus was originally spelled Liberobacter.
Ralstonia virus RSA1 is a virus of the family Myoviridae, genus Aresaunavirus.
Transcription Activator-Like Effector-Likes (TALE-likes) are a group of bacterial DNA binding proteins named for the first and still best-studied group, the TALEs of Xanthomonas bacteria. TALEs are important factors in the plant diseases caused by Xanthomonas bacteria, but are known primarily for their role in biotechnology as programmable DNA binding proteins, particularly in the context of TALE nucleases. TALE-likes have additionally been found in many strains of the Ralstonia solanacearum bacterial species complex, in Paraburkholderia rhizoxinica strain HKI 454, and in two unknown marine bacteria. Whether or not all these proteins form a single phylogenetic grouping is as yet unclear.
Ralstonia pseudosolanacearum is a soil-borne bacterium. It is a vascular phytopathogen that infects host plants through the root system causing wilting disease that causes loss in a wide range of crops. R. pseudosolanacearum is Gram negative and was originally identified as Ralstonia solanacearum, however, in 2014 Safni et al. proposed a taxonomic revision of the Ralstonia solanacearum species complex to reclassify phylotype strains, including R. pseudosolanacearum.
