Pink-Pigmented Facultative Methylotrophs, commonly abbreviated to PPFMs, are bacteria that are members of the genus Methylobacterium and are commonly found in soil, dust, various fresh water supplies and on plant surfaces. [1] Although Gram negative, Methylobacteria often stain gram variable and are easily isolated using methanol-based mineral medium. [2] Their pigmentation, which is frequently pink but may also be yellow or orange, is thought to provide protection from solar UV radiation which damages the DNA of bacteria at low doses because of their small cell size. This color is present due to the carotenoid pigments within the cell. [3]
The metabolism of PPFMs is unusual because, as their name suggests, they are able to utilize C1 compounds such as formaldehyde, methanol and methylamine. [4] PPFM bacteria can undergo methylotrophy, a process in which the bacteria oxidize methanol with the help of the enzymes methanol dehydrogenase (MDH) and pyrroloquinoline quinone (PQQ)-linked protein. [3] In dense and diverse communities like those found in the phyllosphere and rhizosphere, this enables them to utilize nutrients other bacteria cannot, enhancing their competitive ability. In certain environments there are limited concentrations of elements such as carbon and phosphate in a usable form. Research suggests that PPFMs breakdown unusable forms of carbon into usable forms for other species forming symbiotic relationships.
PPFM bacteria form symbiotic relationships with numerous species of plants. PPFMs are horizontally transmitted to the next generation of plants through their seeds. [5] This relationship is beneficial for plants, as the PPFMs produce cytokinins. [6] Plants with more growth showed an increased concentration in cytokinin production, but credit has yet to be given to the bacteria. [5] It has also been established that PPFM symbionts produce additional growth factors such as ethylene, [7] auxins, [8] and gibberellic acid [9] which benefit the plants. This relationship is a model for plant-microbe interactions. As mentioned, PPFMs are known for their ability to utilize methanol as a sole energy source. It has been reported that trees and crop species emit large amounts of the alcohol methanol from their stomata, which potentially attracts symbiotic species. Interestingly, younger trees emit even more methanol which may encourage a healthy population of PPFM from an early stage of growth. Methanol breakdown by PPFMs allows plants to grow in different niches. Without this process, plants would not have access to enough carbon to grow efficiently. Studies also indicate that PPFM can break down additional carbon sources and also utilize phosphate efficiently, [3] potentially providing additional assistance to plants.
Overall, research in this field suggests that a plant's growth, survival, and reproductive success are significantly better when grown symbiotically with PPFMs. So far this relationship is only beneficial to haploid gametophytes, such as liverworts and mosses, but additional relationships are being investigated. There is a global application to this research, implying that PPFMs would be appropriate probiotic for some species of plants. Research by Mark Holland suggests that the normal storage of seeds for market use (after drying in a 50°C oven for 48h) rids the seeds of their native PPFM species. Incubating seeds with PPFM prior to germination encouraged germination and growth compared to controls. [5] Research suggests that this relationship extends to marine and freshwater plant species as well. [5] Additional research in this field will allow scientists to understand the complicated, yet important, relationship between plants and bacteria. PPFMs offer a low-cost biotech application to encourage enhanced growth, reproduction, and preferred characteristics of plant species in numerous environments.
Methylotrophs are a diverse group of microorganisms that can use reduced one-carbon compounds, such as methanol or methane, as the carbon source for their growth; and multi-carbon compounds that contain no carbon-carbon bonds, such as dimethyl ether and dimethylamine. This group of microorganisms also includes those capable of assimilating reduced one-carbon compounds by way of carbon dioxide using the ribulose bisphosphate pathway. These organisms should not be confused with methanogens which on the contrary produce methane as a by-product from various one-carbon compounds such as carbon dioxide. Some methylotrophs can degrade the greenhouse gas methane, and in this case they are called methanotrophs. The abundance, purity, and low price of methanol compared to commonly used sugars make methylotrophs competent organisms for production of amino acids, vitamins, recombinant proteins, single-cell proteins, co-enzymes and cytochromes.
Symbiotic bacteria are bacteria living in symbiosis with another organism or each other. For example, rhizobia living in root nodules of legumes provide nitrogen fixing activity for these plants.
Tibicos, or water kefir, is a traditional fermented drink made with water and a symbiotic culture of bacteria and yeasts (SCOBY) held in a polysaccharide biofilm matrix created by the bacteria. It is sometimes consumed as an alternative to milk-based probiotic drinks or tea-cultured products such as kombucha. Water kefir is typically made as a probiotic homebrew beverage. The finished product, if bottled, will produce a carbonated beverage.
Rhodococcus fascians is a Gram positive bacterial phytopathogen that causes leafy gall disease. R. fascians is the only phytopathogenic member of the genus Rhodococcus; its host range includes both dicotyledonous and monocotyledonous hosts. Because it commonly afflicts tobacco (Nicotiana) plants, it is an agriculturally significant pathogen.
Methylorubrum extorquens is a Gram-negative bacterium. Methylorubrum species often appear pink, and are classified as pink-pigmented facultative methylotrophs, or PPFMs. The wild type has been known to use both methane and multiple carbon compounds as energy sources. Specifically, M. extorquens has been observed to use primarily methanol and C1 compounds as substrates in their energy cycles. It has been also observed that use lanthanides as a cofactor to increase its methanol dehydrogenase activity
Methylobacillus flagellatus is a species of aerobic bacteria.
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.
Methylorubrum populi is an aerobic, pink-pigmented, facultatively methylotrophic, methane-utilizing bacterium isolated from poplar trees. Its type strain is BJ001T.
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.
Methylobacterium gossipiicola is a Gram-negative, aerobic, facultatively methylotrophic bacteria from the genus of Methylobacterium which has been isolated from cotton in Coimbatore in India.
Methylobacterium marchantiae is a facultatively methylotrophic facultative methylotrophy bacteria from the genus of Methylobacterium which has been isolated from the moos Marchantia polymorpha in Bergpark Wilhelmshöhe near Kassel in Germany.
Methylobacterium oryzae is a facultatively methylotrophic and aerobic bacteria from the genus of Methylobacterium which has been isolated from tissues of the rice plant Oryza sativa in Cheongwon in Korea. Methylobacterium oryzae can utilize 1-aminocyclopropane 1-carboxylate. Methylobacterium oryzae can promote plant growth.
Methylobacterium persicinum is a facultatively methylotrophic and aerobic bacteria from the genus of Methylobacterium which has been isolated from the rice plant Oryza sativa in Iksan in Korea.
Methylorubrum thiocyanatum is a facultative methylotroph bacteria from the genus Methylorubrum that has been isolated from soil around the plant Allium aflatunense in Warwickshire, United Kingdom.
Methylobacterium thuringiense is a Gram-negative, aerobic, facultatively methylotrophic and rod-shaped bacteria from the genus of Methylobacterium.
Methylobacterium trifolii is a Gram-negative, aerobic, facultatively methylotrophic and rod-shaped bacteria from the genus of Methylobacterium.
A phytobiome consists of a plant (phyto) situated in its specific ecological area (biome), including its environment and the associated communities of organisms which inhabit it. These organisms include all macro- and micro-organisms living in, on, or around the plant including bacteria, archaea, fungi, protists, insects, animals, and other plants. The environment includes the soil, air, and climate. Examples of ecological areas are fields, rangelands, forests. Knowledge of the interactions within a phytobiome can be used to create tools for agriculture, crop management, increased health, preservation, productivity, and sustainability of cropping and forest systems.
Methylorubrum pseudosasae is a Gram-negative, aerobic, facultatively methylotrophic bacteria from the genus Methylorubrum which has been isolated from bamboo leaves.
Plant root exudates are fluids emitted through the roots of plants. These secretions influence the rhizosphere around the roots to inhibit harmful microbes and promote the growth of self and kin plants.
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".