Variovorax paradoxus | |
---|---|
Scientific classification | |
Domain: | Bacteria |
Phylum: | Pseudomonadota |
Class: | Betaproteobacteria |
Order: | Burkholderiales |
Family: | Comamonadaceae |
Genus: | Variovorax |
Species: | V. paradoxus |
Binomial name | |
Variovorax paradoxus | |
Type strain | |
13-0-1D, ATCC 17713, BCRC 17070, CCM 4467, CCRC 17070, CCUG 1777, CIP 103459, DSM 30034, DSM 66, IAM 12373, IAM 13535, ICPB 3985, IFO 15149, JCM 20526, JCM 20895, KACC 10222, KCTC 1007, KCTC 12459, LGM 1797t1, LMG 11797 t1, LMG 1797, NBRC 15149, NCIB 11964, NCIMB 11964, VKM B-1329 [2] |
Variovorax paradoxus is a gram negative, beta proteobacterium from the genus Variovorax. [1] Strains of V. paradoxus can be categorized into two groups, hydrogen oxidizers and heterotrophic strains, both of which are aerobic. [3] The genus name Vario-vorax (various-voracious; devouring a variety of substrates) and species name para-doxus (contrary-opinion) reflects both the dichotomy of V. paradoxus metabolisms, but also its ability to utilize a wide array of organic compounds. [1]
V. paradoxus cells are curved rods in shape, with dimensions of 0.3-0.6 x 0.7-3.0 μm in size and normally occur as either single or pairs of cells. Typically, cells have 1-3 peritrichous, degenerate flagella. Colonies of V. paradoxus are yellow-green in colour, due to the production of carotenoid pigments, and often have an iridescent sheen. [4] Colony shape is normally convex, round and smooth, but can also display flat, undulate margins. [1] V. paradoxus grows optimally at 30 °C in most growth media, including M9-glucose. On nutrient agar and M9-glucose agar, colonies take 24–48 hours to grow to a few millimetres in size.
Pantothenate is a characteristic carbon source utilized by V. paradoxus; it was the use of this sole carbon source that lead to the isolation of the first known strain of V. paradoxus. [3] Polyhydroxyalkanoates (PHA), including poly-3-hydroxybutyrate (3-PHB), are stored intracellularly by V. paradoxus cells when carbon is abundant and other factors limit growth [3] [4] [5]
The genomes of four strains of V. paradoxus have been sequenced, S110, [6] EPS, [7] B4 [8] and TBEA6. [9] S110 was isolated from the interior of a potato plant and was identified as a degrader of AHLs. This strain has two chromosomes (5.63 and 1.13Mb), a G+C content of 67.4% and a predicted number of 6279 open reading frames (ORF). [6] EPS was isolated from the rhizosphere community of the sunflower (Helianthus annuus), and was initially studied for its motility. It has one chromosome (6.65Mb), a G+C content of 66.48% and a total of 6008 genes identified. [7] The genomes of B4 and TBEA6 were sequenced with specific interest to better understand the strains abilities to degrade mercaptosuccinate and 3,3 -thiodipropionic acid respectively. [8] [9]
Found ubiquitously, V. paradoxus has been isolated from a diverse range of environments including soil, [10] [11] the rhizosphere of numerous plant species, [6] [10] [12] drinking water, [13] ground water, [14] freshwater iron seeps, [15] ferromanganese deposits in carbonate cave systems, [16] deep marine sediments, [17] silver mine spoil, [18] gold-arsenopyrite mine drainage water, [19] rubber tyre leachate [20] and surface snow. [21] In particularly, V. paradoxus is abundant in numerous environments that are contaminated with either recalcitrant organic compounds or heavy metals. V. paradoxus is also commonly found in plant rhizosphere communities and is a known plant growth-promoting bacterium (PGPB). It is from these two types of environments that V. paradoxus has been most extensively studied. [4]
V. paradoxus’s diverse metabolic capabilities enable it to degrade a wide array of recalcitrant organic pollutants including 2,4-dinitrotoluene, aliphatic polycarbonates and polychlorinated biphenyls. Both its catabolic and anabolic capabilities have been suggested for biotechnological use, such as to neutralise or degrade pollutants at contaminated sites. [4]
The role of V. paradoxus in the plant root rhizosphere and surrounding soil has been investigated in several plant species, with implicated growth promoting mechanisms including reducing plant stress, increasing nutrient availability and inhibiting growth of plant pathogens; many of these mechanisms relate to the species catabolic capabilities. [6] In the rhizosphere of pea plants (Pisum sativum), V. paradoxus was shown to increase both growth and yield by degrading the ethylene precursor molecule 1-aminocyclopropane-1-carboxylate (ACC), using a secreted ACC deaminase. [22] Strains of V. paradoxus have also been identified that can degrade N-acyl homoserine-lactones (AHL), microbial signalling molecules involved in quorum sensing. [23] It is hypothesized that this ability could provide a host plant protection from pathogenic infection, with the impact of quorum quenching to reduce virulence in pathogenic strains present. [24]
V. paradoxus is involved in cycling numerous inorganic elements including arsenic, [25] [26] sulfur, [10] manganese [27] [28] and rare earth elements [29] in a range of soil, freshwater and geological environments. In the case of arsenic, V. paradoxus is believed to oxidize As (III) to As (V) as a detoxification mechanism. [25] V. paradoxus has been found in a range of rocky environments including carbonate caves, mine spoil and deep marine sediments, but the role of this organism within these environments is largely unstudied. [16] [17] [18] The species is also tolerant of a large number of heavy metals including cadmium, [30] chromium, cobalt, copper, lead, mercury, nickel, silver, [18] zinc [31] at mM concentrations. [32] Despite this, very little is known about the physiological adaptions V. paradoxus uses to support this tolerance. The sequenced genome of the endophytic strain V. paradoxus S110 provides some clues to the organism's metal tolerance by identifying key molecular machinery in processing metals such as the arsenic reductase complex ArsRBC, metal transporting P1-type ATPases and a chemiosmotic antiporter efflux system similar to CzcCBA of Cupriavidus metallidurans. [6] Cupriavidus species, including C. metallidurans, are well characterised in the field of microbe-metal interactions, and are found within the same order (Burkholderiales) as V. paradoxus. Both the species C. necator and C. metallidurans (when not distinguished as separate species) were originally classified in the genera Alcaligenes along with V. paradoxus (Alcaligenes eutrophus and Alicaligenes paradoxus). [3] [33] This relationship with other heavy metal resistant species may help to partially explain the evolutionary history of V. paradoxus's metal tolerance.
The V. paradoxus strain EPS has been shown capable of swarming motility and biofilm formation. [34] [35] Jamieson et al. demonstrate that altering the carbon and nitrogen sources provided in the swarming agar causes variation in both swarm colony size and morphology. [34] Mutagenesis studies have revealed that the swarming capability of V. paradoxus is largely dependent on a gene involved surfactant production, a type IV pili component and the ShkRS two component system. [35] Dense biofilms of V. paradoxus can be grown in M9 medium with carbon sources including d-sorbitol, glucose, malic acid, mannitol and sucrose and casamino acids. Production of exopolysaccharide was hypothesized to be a controlling factor in biofilm formation. V. paradoxus biofilms take on a honeycomb morphology, as identified in many other species of biofilm forming bacteria. [34]
Pseudomonas fluorescens is a common Gram-negative, rod-shaped bacterium. It belongs to the Pseudomonas genus; 16S rRNA analysis as well as phylogenomic analysis has placed P. fluorescens in the P. fluorescens group within the genus, to which it lends its name.
Sphingomonadaceae are a gram-negative bacterial family of the Alphaproteobacteria. An important feature is the presence of sphingolipids in the outer membrane of the cell wall. The cells are ovoid or rod-shaped. Others are also pleomorphic, i.e. the cells change the shape over time. Some species from Sphingomonadaceae family are dominant components of biofilms.
In microbiology, the phyllosphere is the total above-ground surface of a plant when viewed as a habitat for microorganisms. The phyllosphere can be further subdivided into the caulosphere (stems), phylloplane (leaves), anthosphere (flowers), and carposphere (fruits). The below-ground microbial habitats are referred to as the rhizosphere and laimosphere. Most plants host diverse communities of microorganisms including bacteria, fungi, archaea, and protists. Some are beneficial to the plant, while others function as plant pathogens and may damage the host plant or even kill it.
Nitrospira translate into “a nitrate spiral” is a genus of bacteria within the monophyletic clade of the Nitrospirota phylum. The first member of this genus was described 1986 by Watson et al., isolated from the Gulf of Maine. The bacterium was named Nitrospira marina. Populations were initially thought to be limited to marine ecosystems, but it was later discovered to be well-suited for numerous habitats, including activated sludge of wastewater treatment systems, natural biological marine settings, water circulation biofilters in aquarium tanks, terrestrial systems, fresh and salt water ecosystems, agricultural lands and hot springs. Nitrospira is a ubiquitous bacterium that plays a role in the nitrogen cycle by performing nitrite oxidation in the second step of nitrification. Nitrospira live in a wide array of environments including but not limited to, drinking water systems, waste treatment plants, rice paddies, forest soils, geothermal springs, and sponge tissue. Despite being abundant in many natural and engineered ecosystems Nitrospira are difficult to culture, so most knowledge of them is from molecular and genomic data. However, due to their difficulty to be cultivated in laboratory settings, the entire genome was only sequenced in one species, Nitrospira defluvii. In addition, Nitrospira bacteria's 16S rRNA sequences are too dissimilar to use for PCR primers, thus some members go unnoticed. In addition, members of Nitrospira with the capabilities to perform complete nitrification has also been discovered and cultivated.
Dehalococcoides is a genus of bacteria within class Dehalococcoidia that obtain energy via the oxidation of hydrogen and subsequent reductive dehalogenation of halogenated organic compounds in a mode of anaerobic respiration called organohalide respiration. They are well known for their great potential to remediate halogenated ethenes and aromatics. They are the only bacteria known to transform highly chlorinated dioxins, PCBs. In addition, they are the only known bacteria to transform tetrachloroethene to ethene.
Burkholderia cenocepacia is a Gram-negative, rod-shaped bacterium that is commonly found in soil and water environments and may also be associated with plants and animals, particularly as a human pathogen. It is one of over 20 species in the Burkholderia cepacia complex (Bcc) and is notable due to its virulence factors and inherent antibiotic resistance that render it a prominent opportunistic pathogen responsible for life-threatening, nosocomial infections in immunocompromised patients, such as those with cystic fibrosis or chronic granulomatous disease. The quorum sensing systems CepIR and CciIR regulate the formation of biofilms and the expression of virulence factors such as siderophores and proteases. Burkholderia cenocepacia may also cause disease in plants, such as in onions and bananas. Additionally, some strains serve as plant growth-promoting rhizobacteria.
Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota. It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically important groups of bacteria belong to this class. All members of this class are Gram-negative. It is the most phylogenetically and physiologically diverse class of the Pseudomonadota.
Stenotrophomonas is a genus of Gram-negative bacteria, comprising at least ten species. The main reservoirs of Stenotrophomonas are soil and plants. Stenotrophomonas species range from common soil organisms to opportunistic human pathogens ; the molecular taxonomy of the genus is still somewhat unclear.
Shewanella oneidensis is a bacterium notable for its ability to reduce metal ions and live in environments with or without oxygen. This proteobacterium was first isolated from Lake Oneida, NY in 1988, hence its name.
The Xanthobacteraceae are a family of bacteria that includes Azorhizobium, a genus of rhizobia. Xanthobacteraceae bacteria are diverse and Gram-negative, rod-shaped, and may be motile or non-motile depending on the specific bacteria. Their cells range in size from 0.4–1.0 × 0.8–6 μm, but when grown in the presence of alcohol as the sole carbon source, they can reach up to 10 μm in length. These bacteria do not form spores and have opaque, slimy colonies that appear slightly yellow due to the presence of zeaxanthin dirhamnoside.
Alteromonas macleodii is a species of widespread marine bacterium found in surface waters across temperate and tropical regions. First discovered in a survey of aerobic bacteria in 1972, A. macleodii has since been placed within the phylum Pseudomonadota and is recognised as a prominent component of surface waters between 0 and 50 metres. Alteromonas macleodii has a single circular DNA chromosome of 4.6 million base pairs. Variable regions in the genome of A. macleodii confer functional diversity to closely related strains and facilitate different lifestyles and strategies. Certain A. macleodii strains are currently being explored for their industrial uses, including in cosmetics, bioethanol production and rare earth mining.
"Candidatus Scalindua" is a bacterial genus, and a proposed member of the order Planctomycetales. These bacteria lack peptidoglycan in their cell wall and have a compartmentalized cytoplasm. They are ammonium oxidizing bacteria found in marine environments.
Geobacter sulfurreducens is a gram-negative metal- and sulphur-reducing proteobacterium. It is rod-shaped, aerotolerant anaerobe, non-fermentative, has flagellum and type four pili, and is closely related to Geobacter metallireducens. Geobacter sulfurreducens is an anaerobic species of bacteria that comes from the family of bacteria called Geobacteraceae. Under the genus of Geobacter, G. sulfurreducens is one out of twenty different species. The Geobacter genus was discovered by Derek R. Lovley in 1987. G. sulfurreducens was first isolated in Norman, Oklahoma, USA from materials found around the surface of a contaminated ditch.
Acidobacterium capsulatum is a bacterium. It is an acidophilic chemoorganotrophic bacterium containing menaquinone. It is gram-negative, facultative anaerobic, mesophilic, non-spore-forming, capsulated, saccharolytic and rod-shaped. It is also motile by peritrichous flagella. Its type strain is JCM 7670.
Ruegeria pomeroyi is a species of Gram-negative, rod-shaped, aerobic dimethylsulfoniopropionate-demethylating bacterium. Its type strain is DSS-3T. Its genome has been sequenced.
The root microbiome is the dynamic community of microorganisms associated with plant roots. Because they are rich in a variety of carbon compounds, plant roots provide unique environments for a diverse assemblage of soil microorganisms, including bacteria, fungi, and archaea. The microbial communities inside the root and in the rhizosphere are distinct from each other, and from the microbial communities of bulk soil, although there is some overlap in species composition.
Desulfovibrio alcoholivorans is a bacterium from the genus of Desulfovibrio which has been isolated from alcohol industry waste water in France.
Mycorrhiza helper bacteria (MHB) are a group of organisms that form symbiotic associations with both ectomycorrhiza and arbuscular mycorrhiza. MHBs are diverse and belong to a wide variety of bacterial phyla including both Gram-negative and Gram-positive bacteria. Some of the most common MHBs observed in studies belong to the genera Pseudomonas and Streptomyces. MHBs have been seen to have extremely specific interactions with their fungal hosts at times, but this specificity is lost with plants. MHBs enhance mycorrhizal function, growth, nutrient uptake to the fungus and plant, improve soil conductance, aid against certain pathogens, and help promote defense mechanisms. These bacteria are naturally present in the soil, and form these complex interactions with fungi as plant root development starts to take shape. The mechanisms through which these interactions take shape are not well-understood and needs further study.
Acinetobacter baylyi is a bacterial species of the genus Acinetobacter. The species designation was given after the discovery of strains in activated sludge in Victoria, Australia, in 2003. A. baylyi is named after the late Dr. Ronald Bayly, an Australian microbiologist who contributed significantly to research on aromatic compound catabolism in diverse bacteria. The new species designation, in 2003, was found to apply to an already well-studied Acinetobacter strain known as ADP1, a derivative of a soil isolate characterized in 1969. Strain ADP1 was previously designated Acinetobacter sp. and Acinetobacter calcoaceticus. Research, particularly in the field of genetics, has established A. baylyi as a model organism.
The plant microbiome, also known as the phytomicrobiome, plays roles in plant health and productivity and has received significant attention in recent years. The microbiome has been defined as "a characteristic microbial community occupying a reasonably well-defined habitat which has distinct physio-chemical properties. The term thus not only refers to the microorganisms involved but also encompasses their theatre of activity".