Formation of melanin pigment by a mutant of Bacillus thuringiensis H-14

Hoti, S.L.; Balaraman, K

doi:10.1099/00221287-139-10-2365

Cited by 49 publications

(43 citation statements)

References 27 publications

(16 reference statements)

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“…A similar pigmented phenotype was previously described for two different B. thuringiensis strains exposed to a mutagenic agent (14,23,25). These two strains produced a brown pigment identical to synthetic melanin obtained by the persulfate oxidation of tyrosine and were more toxic to insects than were the parental strains from which they were derived.…”

Section: Discussionmentioning

confidence: 55%

“…Several B. thuringiensis mutants producing a melanin pigment and displaying higher-than-normal levels of toxicity have been described elsewhere (14,23,25) or for other pathogenic species of bacteria (5,15). Assuming a possible common biosynthetic pathway (or regulation mechanism) for pigment and ␤-exotoxin I production in strain 407-1(Cry Ϫ )(Pig ϩ ), we performed Tn10 insertion mutagenesis, with the shuttle vector pIC333, and used pigment production as a genetic marker, for the screening of nonpigmented and possibly nontoxic mutant clones.…”

Section: Resultsmentioning

confidence: 99%

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An ABC Transporter from Bacillus thuringiensis Is Essential for β-Exotoxin I Production

et al. 2002

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␤-Exotoxin I is a nonspecific insecticidal metabolite secreted by some Bacillus thuringiensis strains. Several studies of B. thuringiensis strains that have lost the capacity to produce ␤-exotoxin I have suggested that there is a strong correlation between high levels of ␤-exotoxin I production and the ability to synthesize crystal proteins. In this study, we showed that a mutant strain, B. thuringiensis 407-1(Cry ؊ )(Pig ؉ ), with no crystal gene, produced considerable amounts of ␤-exotoxin I together with a soluble brown melanin pigment. Therefore, ␤-exotoxin I production can take place after a strain has lost the plasmids bearing the cry genes, which suggests that these curable plasmids probably contain determinants involved in the regulation of ␤-exotoxin I production. Using a mini-Tn10 transposon, we constructed a library of strain 407-1(Cry ؊ )(Pig ؉ ) mutants. We screened for nonpigmented mutants with impaired ␤-exotoxin I production and identified a genetic locus harboring two genes (berA and berB) essential for ␤-exotoxin I production. The deduced amino acid sequence of the berA gene displayed significant similarity to the ATP-binding domains of the DRI (drug resistance and immunity) family of ATP-binding cassette (ABC) proteins involved in drug resistance and immunity to bacteriocins and lantibiotics. The berB gene encodes a protein with six putative transmembrane helices, which probably constitutes the integral membrane component of the transporter. The demonstration that berAB is required for ␤-exotoxin I production and/or resistance in B. thuringiensis adds an adenine nucleotide analog to the wide range of substrates of the superfamily of ABC proteins. We suggest that berAB confers ␤-exotoxin I immunity in B. thuringiensis, through active efflux of the molecule.

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Section: Discussionmentioning

confidence: 55%

Section: Resultsmentioning

confidence: 99%

An ABC Transporter from Bacillus thuringiensis Is Essential for β-Exotoxin I Production

et al. 2002

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“…kurstaki and other strains by successive rounds of UV irradiation (Hoti and Balaraman, 1993;Pater et al, 1996;Saxena et al, 2002). Compared with their parent strains, these Bt mutants were more resistant to UV irradiation, but some of them lost their toxin-encoding genes.…”

Section: Introductionmentioning

confidence: 95%

Characterization of melanin produced by a wild-type strain of Bacillus thuringiensis

Chen

Yinyue

Wang

et al. 2004

J. Gen. Appl. Microbiol.

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Bt L-7601 is a UV resistant wild-type strain, which belongs to Bacillus thuringiensis subsp. dendrolimus serotype H4a4b. It was isolated from nature, and produced a dark brown pigment during the exponential phase of growth. Bt L-7601 had the ability to produce pigment in a general nutrition-abundant medium, which had no L-tyrosine. The pigment was identified as melanin based on chemical testing, its light absorbance, and FT-IR analysis. Bt L-7601 has a strong resistance to UV light. After 30 min irradiation its survival rate was 17 times higher than that of the strain B. thuringiensis subsp. colmeri 15A3, which had no pigment. Results of the bioassays of residual insecticidal activity of Bt formulation with and without pigment produced by Bt L-7601 against larvae of Helicoverpa armigera and Spodoptera exigua after exposure to UV irradiation showed that the pigment is an excellent UV protective agent for the insecticidal proteins.

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“…Melanin may protect bacteria and fungi from different types of stress, including toxic products such as H 2 O 2 , pesticides, heavy metals and antibiotics (Hoti & Balaraman, 1993;Hullo et al, 2001;Nosanchuk & Casadevall, 2006).…”

Section: Effect Of Hmga Inactivation On Resistance To H 2 O 2 and Antmentioning

confidence: 99%

Inactivation of the hmgA gene of Pseudomonas aeruginosa leads to pyomelanin hyperproduction, stress resistance and increased persistence in chronic lung infection

et al. 2009

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Clinical isolates of Pseudomonas aeruginosa that hyperproduce a dark-brown pigment are quite often found in the lungs of chronically infected patients, suggesting that they may have an adaptive advantage in chronic infections. We have screened a library of random transposon insertions in P. aeruginosa. Transposon insertions resulting in the hyperproduction of a darkbrown pigment were found to be located in the hmgA gene, which putatively encodes the enzyme homogentisate-1,2-dioxygenase. Complementation studies indicate that hmgA disruption is responsible for the hyperproduction of pyomelanin in both laboratory and clinical isolates. A relationship between hmgA disruption and adaptation to chronic infection was explored and our results show that the inactivation of hmgA produces a slight reduction of killing ability in an acute murine model of lung infection. On the other hand, it also confers decreased clearance and increased persistence in chronic lung infections. Whether pyomelanin production is the cause of the increased adaptation to chronicity or just a side effect of hmgA inactivation is a question to be studied in future; however, this adaptation is consistent with the higher resistance to oxidative stress conferred in vitro by the pyomelanin pigment. Our results clearly demonstrate that hmgA inactivation leads to a better adaptation to chronic infection, and strongly suggest that this mechanism may be exploited in naturally occurring P. aeruginosa strains.

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Formation of melanin pigment by a mutant of Bacillus thuringiensis H-14

Cited by 49 publications

References 27 publications

An ABC Transporter from Bacillus thuringiensis Is Essential for β-Exotoxin I Production

An ABC Transporter from Bacillus thuringiensis Is Essential for β-Exotoxin I Production

Characterization of melanin produced by a wild-type strain of Bacillus thuringiensis

Inactivation of the hmgA gene of Pseudomonas aeruginosa leads to pyomelanin hyperproduction, stress resistance and increased persistence in chronic lung infection

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