Lysobacter

The genus ''Lysobacter'' belongs to the family Xanthomonadaceae within the Gammaproteobacteria and includes at least 46 named species, including: ''Lysobacter enzymogenes, L. antibioticus, L. gummosus, L. brunescens, L. defluvii, L. niabensis, L. niastensis, L. daejeonensis, L. yangpyeongensis, L. koreensis, L. concretionis, L. spongiicola'', and ''L. capsici''.Bae, H. S., W. T. Im, and S. T. Lee. 2005. ''Lysobacter concretionis'' sp. nov., isolated from anaerobic granules in an upflow anaerobic sludge blanket reactor. Int J Syst Evol Microbiol 55:1155–61.Weon, H. Y., B. Y. Kim, Y. K. Baek, S. H. Yoo, S. W. Kwon, E. Stackebrandt, and S. J. Go. 2006. Two novel species, ''Lysobacter daejeonensis'' sp. nov. and ''Lysobacter yangpyeongensis'' sp. nov., isolated from Korean greenhouse soils. Int J Syst Evol Microbiol 56:947-51. ''Lysobacter'' spp. were originally grouped with myxobacteria because they shared the distinctive trait of gliding motility, but they uniquely display a number of traits that distinguish them from other taxonomically and ecologically related microbes including high genomic G+C content (typically ranging between 65 and 72%) and the lack of flagella.Christensen, P., and F. Cook. 1978. ''Lysobacter'', a new genus of nonfruiting, gliding bacteria with a high base ratio. International Journal of Systematic Bacteriology 28:367–393. The feature of gliding motility alone has piqued the interest of many, since the role of gliding bacteria in soil ecology is poorly understood. In addition, while a number of different mechanisms have been proposed for gliding motility among a wide range of bacterial species, the genetic mechanism in ''Lysobacter'' remains unknown. Members of the ''Lysobacter'' group have gained broad interest for production of extracellular enzymes. The group is also regarded as a rich source for production of novel antibiotics, such as β-lactams containing substituted side chains, macrocyclic lactams and macrocyclic peptide or depsipeptide antibiotics like the katanosins.

Habitat

''Lysobacter'' spp. have been described as ubiquitous inhabitants of soil and water. Their presence has been largely ignored, since members often are minor components in sample screenings when using conventional isolation procedures. However, because of improved molecular methods of identification and better descriptions for the genus, their agricultural relevance is becoming increasingly evident, especially as members of ecologically significant microbial communities associated with soil and plants.Sullivan, R. F., M. A. Holtman, G. J. Zylstra, J. F. White, and D. Y. Kobayashi. 2003. Taxonomic positioning of two biological control agents for plant diseases as ''Lysobacter enzymogenes'' based on phylogenetic analysis of 16S rDNA, fatty acid composition and phenotypic characteristics. Journal of Applied Microbiology 94:1079–1086. Recent evidence suggests ''Lysobacter'' spp. may occupy a wide range of ecological niches beyond those associated with plants, including a broad range of 'extreme' environments. For example, 16S rDNA phylogenetic analyses show ''Lysobacter'' clades that include sequences obtained from hydrothermal vents, isolates from Mt. Pinatubo mud flows and upflow anaerobic blanket sludge reactors, and an iron-oxidizing, microaerophilic lithotroph.Folman, L. B., J. Postma, and J. A. van Veen. 2003. Characterisation of ''Lysobacter enzymogenes'' (Christensen and Cook 1978) strain 3.1T8, a powerful antagonist of fungal diseases of cucumber. Microbiological Research 158:107–115.

''Lysobacter gummosus'' was discovered living on the skin of redback salamanders and producing 2,4-diacetylphloroglucinol, a chemical which inhibits the growth of certain pathogenic fungi.Brucker RM, Baylor CM, Walters RL, Lauer A, Harris RN, Minbiole KPC. 2008. The identification of 2,4-diacetylphloroglucinol as an antifungal metabolite produced by cutaneous bacteria of the salamander Plethodon cinereus. Journal of Chemical Ecology 34(1):39–43.

Biological control

The potential of ''Lysobacter'' species as biological control agents for plant diseases has been recognized. Among ''L. enzymogenes'' strains, C3 is the most thoroughly characterized strain at both the molecular and biological levels. The ecological versatility of the strain is reflected by the range of diseases it is able to control, as well as the various plant hosts and plant parts it is capable of colonizing. For example, ''L. enzymogenes'' strain C3 (erroneously identified as ''Stenotrophomonas maltophilia'') has been reported to control foliar diseases such as leaf spot of tall fescue caused by ''Bipolaris sorokiniana'', bean rust caused by ''Uromyces appendiculatus'' and ''Fusarium'' head blight of wheat. ''L. enzymogenes'' strain C3 also has been reported to suppress soilborne diseases, such as brown patch in turfgrass caused by ''Rhizoctonia solani'', the seedling disease ''Pythium'' damping-off of sugarbeet and summer patch disease of Kentucky bluegrass caused by the root-infecting ''Magnaporthe poae''. ''Lysobacter'' sp. SB-K88 has been found to suppress damping-off disease in sugar beet and spinach through antibiosis and characteristic root colonization in perpendicular fashio
Islam et al. (2005).

Disease-suppressive soils

''Lysobacter'' species have also been isolated from soils suppressive to ''Rhizoctonia solani''. Clay soils with natural suppressiveness against ''Rhizoctonia'' contained higher numbers of antagonistic isolates of ''L. gummosus'', ''L. antibioticus'', and/or ''L. capsici''. Although the mechanism behind this phenomenon is not yet understood, it appeared that growing grass/clover increased the number of these ''Lysobacter'' species, as well as the ''Rhizoctonia'' suppressiveness.

Mechanisms of antagonism

Originally characterized as a biological control agent for plant diseases, ''L. enzymogenes'' strain C3 is unique in that it expresses a wide range of mechanisms contributing to microbial antagonism and biological control that are not shared by all strains of the species. The strain produces numerous extracellular enzymes that contribute to biocontrol activity, including multiple forms of β-1,3-glucanases and chitinases. The strain also has been demonstrated to induce systemic resistance in certain plants, protecting them from pathogen infection. In addition, recent studies have indicated important roles for secondary metabolites with antibiotic activity and biosurfactant activity in fungal antagonism.Kobayashi, D. Y., and G. Y. Yuen. 2005. The role of ''clp''-regulated factors in antagonism against ''Magnaporthe poae'' and biological control of summer patch disease of Kentucky bluegrass by ''Lysobacter enzymogenes'' C3. Can J Microbiol 51:719-23. Several of these traits are globally controlled by a regulator encoded by the ''clp'' gene. Mutations in ''clp'' are intriguing for two reasons. First, the mutant phenotype implies that a broad range of genes is involved in secreted antimicrobials associated with the ''clp'' regulon, many of which remain unidentified. The second is that mutations in ''clp'' result in significant loss of extracellular enzyme activities and antimicrobial activity displayed by ''L. enzymogenes'' strain C3. These activities normally are phenotypically overwhelming and often lead to masking of other phenotypes in standard assays, making mutation effects of non-related genes difficult or nearly impossible to evaluate. However, strains harboring ''clp'' gene mutations provide a means to separate ''clp''-regulated phenotypes from others (such as that describe below), thus making their evaluation feasible.
Biological control and mode of actions of disease suppression by ''Lysobacter'' spp. has been reviewe
Islam 2011

''Lysobacter'' genetics

''L. enzymogenes'' strain C3 is a genetically tractable strain allowing for easy construction of gene knockouts, supporting its use as a model genetic system for unraveling the molecular basis of pathogenicity, as well as identifying mechanisms of microbial antagonism and biological control. Indeed, a number of derivative strains of ''L. enzymogenes'' strain C3 already have been constructed, including mutants affected in structural genes encoding enzyme activities, the regulatory ''clp'' gene and various combinations thereof.Palumbo, J. D., G. Y. Yuen, C. C. Jochum, K. Tatum, and D. Y. Kobayashi. 2005. Mutagenesis of β-1,3-glucanase genes in ''Lysobacter enzymogenes'' strain C3 results in reduced biological control activity toward ''Bipolaris'' leaf spot of tall fescue and ''Pythium'' damping-off of sugar beet. Phytopathology 95:701–707.Kobayashi, D. Y., R. M. Reedy, J. D. Palumbo, J.-M. Zhou, and G. Y. Yuen. 2005. A ''clp'' gene homologue belonging to the ''crp'' gene family globally regulates lytic enzyme production, antimicrobial activity, and biological control activity expressed by ''Lysobacter enzymogenes'' strain C3. Appl. Environ. Microbiol. 71:261–269.

Species

The genus has 46 known species (July 2018):''Lysobacter korlensis sp. nov. and Lysobacter burgurensis sp. nov., isolated from soil''. door Lei Zhang e.a. (2011, International Journal of Systematic and Evolutionary Microbiology)
*''Lysobacter aestuarii''
*''Lysobacter agri''
*''Lysobacter antibioticus''
*''Lysobacter arseniciresistens''
*''Lysobacter brunescens''
*''Lysobacter burgurensis''
*''Lysobacter capsici''
*''Lysobacter caeni''
*''Lysobacter cavernae''
*''Lysobacter concretionis''
*''Lysobacter daejeonensis''
*''Lysobacter defluvii''
*''Lysobacter dokdonensis''
*''Lysobacter enzymogenes''
*'' Lysobacter erysipheiresistens''
*''Lysobacter firmicutimachus''
*''Lysobacter fragariae''
*'' Lysobacter ginsengisoli''
*''Lysobacter gummosus''
*''Lysobacter hankyongensis''
*''Lysobacter humi''
*''Lysobacter koreensis''
*''Lysobacter korlensis''
*''Lysobacter lycopersici''
*''Lysobacter maris''
*''Lysobacter mobilis''
*''Lysobacter niabensis''
*''Lysobacter niastensis''
*''Lysobacter novalis''
*'' Lysobacter olei''
*''Lysobacter oligotrophicus''
*''Lysobacter oryzae''
*''Lysobacter panacisoli''
*''Lysobacter panaciterrae''
*'' Lysobacter rhizophilus''
*''Lysobacter rhizosphaerae''
*''Lysobacter ruishenii''
*''Lysobacter sediminicola''
*''Lysobacter silvestris''
*''Lysobacter solanacearum''
*''Lysobacter soli''
*''Lysobacter spongiicola''
*''Lysobacter terrae''
*''Lysobacter terricola''
*''Lysobacter thermophilus''
*'' Lysobacter tolerans''
*''Lysobacter ximonensis''
*''Lysobacter xinjiangensis''
*''Lysobacter yangpyeongensis''

References

{{Taxonbar, from=Q4518042

Xanthomonadales
Bacteria genera