Typically, chloramphenicol at 50 μg/mL is used to select against the wild type strain, while a genetic transformant of L. This is a surprising finding because chloramphenicol is one of the few antibiotic selection markers currently used in genetic manipulation in L. enzymogenes was able to survive in media containing chloramphenicol at 5 μg/mL or lower concentrations, and the OD 600 can reach 1.1 after 3 days of incubation, which is also the normal cell density when incubated without any antibiotics. In the process of investigating the antibiotic resistance in Lysobacter, we found that L. The finding could also have important implications in microbial ecology and agricultural application of the whole genus. An understanding of this mechanism is important because this knowledge could lead to new methods in genetic manipulation of this new emerging biocontrol agent. Despite the potential as a new source of bioactive natural products and biocontrol agent, the majority of Lysobacter species remain unexplored, and the mechanism behind this very broad intrinsic antibiotic resistance is not known. This is a fairly unusual property for a group of ubiquitous environmental bacteria. However, Lysobacter species are naturally resistant to antibiotics commonly used in genetic selection in bacteria, such as kanamycin, ampicillin, streptomycin, tetracycline, and rifampin. enzymogenes is a genetically tractable species allowing for construction of gene knockouts, supporting its utility as a genetic model system for unraveling the molecular basis for mechanisms of microbial antagonism, biological control and natural products biosynthesis. Īs the most thoroughly characterized strain at both the molecular and biological levels, L. enzymogenes is considered a promising biocontrol agent against plant diseases caused by fungi, peronosporomycetes, nematodes, and bacteria, such as leaf spot of tall fescue caused by Bipolaris sorokiniana, bean rust caused by Uromyces appendiculatus and Fusarium head blight of wheat. enzymogenes and has a novel mode of action against fungi. HSAF is the predominant antifungal compound produced by L. The latter group is particularly interesting because it has a distinct structure and unusual mode of action (Fig. Hybrid peptide-polyketides are also found in these bacteria, such as the cephem-type β-lactam cephabacins and the antifungal compounds HSAF and analogs. These include multiple forms of β-1,3-glucanases and chitinases and potent antibiotics anti-MRSA cyclic peptides, such as lysobactin, tripropeptins, and WAP-8294A. Several Lysobacter species are prolific producers of lytic enzymes and bioactive natural products. Recent evidences also suggested that Lysobacter may occupy a wide range of ecological niches, including a broad range of ‘extreme’ environments. As members of ecologically significant microbial communities ubiquitous in soil and aquatic environments, their agricultural relevance is becoming increasingly evident. Lysobacter is a genus of Gram-negative bacteria with high genomic G + C content ranging between 65 and 72%. Because Lysobacter are ubiquitous inhabitants of soil and water, the finding may have important implications in understanding microbial competitions and bioactive natural product regulation. enzymogenes contains a pool of unusual acyl donors for enzymatic modification of chloramphenicol that confers the resistance, which may involve the Clp-GNAT regulatory system. enzymogenes led to nearly no growth in media containing chloramphenicol, whereas a complementation of clp restored the chloramphenicol acylation as well as antibiotic HSAF production in the clp mutant. Furthermore, a mutation of a global regulator gene ( clp) or a Gcn5-related N-acetyltransferase (GNAT) gene in L. The compounds included chloramphenicol 3'-isobutyrate ( 1), a new compound chloramphenicol 1'-isobutyrate ( 2), and a rare chloramphenicol 3'-isovalerate ( 3). Three chloramphenicol derivatives ( 1– 3) with an unusual acylation pattern were identified in a cat-containing mutant of L. enzymogenes, the most studied species of this genus, could still grow in the presence of a low concentration of chloramphenicol. Previously, we have used chloramphenicol acetyltransferase gene ( cat) as a selection marker in genetic manipulation of natural product biosynthetic genes in Lysobacter, because chloramphenicol is one of the two common antibiotics that Lysobacter are susceptible to. These bacteria are intrinsically resistant to many antibiotics, but the mechanisms behind the antibiotic resistance have not been investigated. The environmental gliding bacteria Lysobacter are emerging as a new group of biocontrol agents due to their prolific production of lytic enzymes and potent antibiotic natural products.
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