Polymyxins are antibiotics. Polymyxins B and E are used in the treatment of Gram-negative bacterial infections. They work mostly by breaking up the bacterial cell membrane. They are part of a broader class of molecules called nonribosomal peptides.
Colistin, also known as polymyxin E, is an antibiotic medication used as a last-resort treatment for multidrug-resistant Gram-negative infections including pneumonia. These may involve bacteria such as Pseudomonas aeruginosa, Klebsiella pneumoniae, or Acinetobacter. It comes in two forms: colistimethate sodium can be injected into a vein, injected into a muscle, or inhaled, and colistin sulfate is mainly applied to the skin or taken by mouth. Colistimethate sodium is a prodrug; it is produced by the reaction of colistin with formaldehyde and sodium bisulfite, which leads to the addition of a sulfomethyl group to the primary amines of colistin. Colistimethate sodium is less toxic than colistin when administered parenterally. In aqueous solutions it undergoes hydrolysis to form a complex mixture of partially sulfomethylated derivatives, as well as colistin. Resistance to colistin began to appear as of 2015.
An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; however, most of the endophyte/plant relationships are not well understood. Some endophytes may enhance host growth and nutrient acquisition and improve the plant's ability to tolerate abiotic stresses, such as drought, and decrease biotic stresses by enhancing plant resistance to insects, pathogens and herbivores. Although endophytic bacteria and fungi are frequently studied, endophytic archaea are increasingly being considered for their role in plant growth promotion as part of the core microbiome of a plant.
Diazotrophs are bacteria and archaea that fix atmospheric nitrogen (N2) in the atmosphere into bioavailable forms such as ammonia.
Paenibacillus is a genus of facultative anaerobic, endospore-forming bacteria, originally included within the genus Bacillus and then reclassified as a separate genus in 1993. Bacteria belonging to this genus have been detected in a variety of environments, such as: soil, water, rhizosphere, vegetable matter, forage and insect larvae, as well as clinical samples. The name reflects: Latin paene means almost, so the paenibacilli are literally "almost bacilli". The genus includes P. larvae, which causes American foulbrood in honeybees, P. polymyxa, which is capable of fixing nitrogen, so is used in agriculture and horticulture, the Paenibacillus sp. JDR-2 which is a rich source of chemical agents for biotechnology applications, and pattern-forming strains such as P. vortex and P. dendritiformis discovered in the early 90s, which develop complex colonies with intricate architectures as shown in the pictures:
Polymyxin B, sold under the brand name Poly-Rx among others, is an antibiotic used to treat meningitis, pneumonia, sepsis, and urinary tract infections. While it is useful for many Gram negative infections, it is not useful for Gram positive infections. It can be given by injection into a vein, muscle, or cerebrospinal fluid or inhaled. The injectable form is generally only used if other options are not available. It is also available as the combinations bacitracin/polymyxin B and neomycin/polymyxin B/bacitracin for use on the skin.
Pseudomonas lini is a fluorescent, Gram-negative, rod-shaped bacterium isolated from rhizospheric soil in France. The type strain is CFBP 5737, though there are also eight other strains known. This bacterium has also been isolated from endophytic tissues of lodgepole pine trees growing on gravel mining sites with potential to perform biological nitrogen fixation and plant growth promotion.
Pseudomonas migulae is a fluorescent, Gram-negative, rod-shaped bacterium isolated from natural mineral waters in France. This bacterium has also been isolated from endophytic tissues of lodgepole pine trees growing on gravel mining sites with potential to perform biological nitrogen fixation and plant growth promotion. Based on 16S rRNA analysis, P. migulae has been placed in the P. fluorescens group.
Paraburkholderia phytofirmans is a species of bacteria. They have been reported to colonize endophytic tissues of hybrid spruce and lodgepole pine with a strong potential to perform biological nitrogen fixation and plant growth promotion.
Caballeronia sordidicola is a species of bacteria which has been reported to perform biological nitrogen fixation and promote plant growth
Rhizobacteria are root-associated bacteria that can have a detrimental, neutral or beneficial effect on plant growth. The name comes from the Greek rhiza, meaning root. The term usually refers to bacteria that form symbiotic relationships with many plants (mutualism). Rhizobacteria are often referred to as plant growth-promoting rhizobacteria, or PGPRs. The term PGPRs was first used by Joseph W. Kloepper in the late 1970s and has become commonly used in scientific literature.
Microbial inoculants, also known as soil inoculants or bioinoculants, are agricultural amendments that use beneficial rhizosphericic or endophytic microbes to promote plant health. Many of the microbes involved form symbiotic relationships with the target crops where both parties benefit (mutualism). While microbial inoculants are applied to improve plant nutrition, they can also be used to promote plant growth by stimulating plant hormone production. Although bacterial and fungal inoculants are common, inoculation with archaea to promote plant growth is being increasingly studied.
Polypeptide antibiotics are a chemically diverse class of anti-infective and antitumor antibiotics containing non-protein polypeptide chains. Examples of this class include actinomycin, bacitracin, colistin, and polymyxin B. Actinomycin-D has found use in cancer chemotherapy. Most other polypeptide antibiotics are too toxic for systemic administration, but can safely be administered topically to the skin as an antiseptic for shallow cuts and abrasions.
A biofertilizer is a substance which contains living micro-organisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Biofertilizers add nutrients through the natural processes of nitrogen fixation, solubilizing phosphorus, and stimulating plant growth through the synthesis of growth-promoting substances. The micro-organisms in biofertilizers restore the soil's natural nutrient cycle and build soil organic matter. Through the use of biofertilizers, healthy plants can be grown, while enhancing the sustainability and the health of the soil. Biofertilizers can be expected to reduce the use of synthetic fertilizers and pesticides, but they are not yet able to replace their use. As of 2024, more than 340 biofertilizer products have been approved for commercial use in the US.
Paenibacillus vortex is a species of pattern-forming bacteria, first discovered in the early 1990s by Eshel Ben-Jacob's group at Tel Aviv University. It is a social microorganism that forms colonies with complex and dynamic architectures. P. vortex is mainly found in heterogeneous and complex environments, such as the rhizosphere, the soil region directly influenced by plant roots.
Herbaspirillum seropedicae is a betaproteobacteria which is an endophytic diazotroph and forms nitrogen-fixing associations with maize, rice, sorghum, sugar cane, bananas (Musa) and pineapple. H. seropedicae is a potential nitrogen biofertilizer. Studies have shown that rice with H. seropedicae inoculated increases the yield to an equivalent of 40 kg N/ha.
Caballeronia udeis is a bacterium from the genus Caballeronia and family Burkholderiaceae which has been reported to perform biological nitrogen fixation and promote plant growth
Paenibacillus macerans is a diazotroph bacterium found in soil and plants capable of nitrogen fixation and fermentation. This bacteria was originally discovered in 1905 by an Austrian biologist named Schardinger and thought to be a bacillus.
Paraburkholderia is a genus of Pseudomonadota that are gram negative, slightly curved rods that are motile by means of flagella. They have been reported to colonize endophytic tissues of hybrid spruce and lodgepole pine with a strong potential to perform biological nitrogen fixation and plant growth promotion. Unlike Burkholderia species, Paraburkholderia members are not commonly associated with human infection. Paraburkholderia members form a monophyletic clade within the Burkholderiaceae family, which is what prompted their distinction as a genus independent from Burkholderia species, in combination with the finding of robust conserved signature indels which are unique to Paraburkholderia species, and are lacking in members of the genus Burkholderia. These CSIs distinguish the genus from all other bacteria. Additionally, the CSIs that were found to be shared by Burkholderia species are absent in Paraburkholderia, providing evidence of separate lineages.
Caballeronia is a genus of bacteria from the family of Burkholderiaceae which has been reported to perform biological nitrogen fixation and promote plant growth
