Gajender Aleti - Academia.edu (original) (raw)

Papers by Gajender Aleti

Research paper thumbnail of Surfactin variants mediate species-specific biofilm formation and root colonization inBacillus

Environmental Microbiology, 2016

Cyclic lipopeptides (cLP) and especially surfactins produced by Bacillus spp. trigger biofilm for... more Cyclic lipopeptides (cLP) and especially surfactins produced by Bacillus spp. trigger biofilm formation and root colonization and are crucial for biocontrol activity and systemic resistance in plants. Bacillus atrophaeus 176s isolated from the moss Tortella tortuosa produces the cLP fengycins, iturins and surfactins, possesses antifungal activities and can protect tomato, lettuce and sugar beet against Rhizoctonia solani infection. In B. atrophaeus we identified for the first time the variant surfactin C, which differs from surfactin A produced by B. subtilis and B. amyloliquefaciens by an isoleucine instead of a leucine at position 7 of the lipopeptide backbone. The analysis of the complete surfactin gene clusters revealed that the dissimilarity is encoded in the adenylation domain of srfC and show that surfactin variations are distributed in a species-specific manner in bacilli. We demonstrate that the surfactin A and C with subtle structural differences have varying signal strengths on biofilm formation and root colonization and act specifically on the respective producing strain. This became evident as biofilm formation and root colonization but not swarming motility in surfactin biosynthesis mutants was restored differentially in the presence of exogenously supplemented cognate and non-cognate surfactin variants.

Research paper thumbnail of Genome mining: Prediction of lipopeptides and polyketides from Bacillus and related Firmicutes

Computational and Structural Biotechnology Journal, 2015

Bacillus and related genera in the Bacillales within the Firmicutes harbor a variety of secondary... more Bacillus and related genera in the Bacillales within the Firmicutes harbor a variety of secondary metabolite gene clusters encoding polyketide synthases and non-ribosomal peptide synthetases responsible for remarkable diverse number of polyketides (PKs) and lipopeptides (LPs). These compounds may be utilized for medical and agricultural applications. Here, we summarize the knowledge on structural diversity and underlying gene clusters of LPs and PKs in the Bacillales. Moreover, we evaluate by using published prediction tools the potential metabolic capacity of these bacteria to produce type I PKs or LPs. The huge sequence repository of bacterial genomes and metagenomes provides the basis for such genome-mining to reveal the potential for novel structurally diverse secondary metabolites. The otherwise cumbersome task to isolate often unstable PKs and deduce their structure can be streamlined. Using web based prediction tools, we identified here several novel clusters of PKs and LPs from genomes deposited in the database. Our analysis suggests that a substantial fraction of predicted LPs and type I PKs are uncharacterized, and their functions remain to be studied. Known and predicted LPs and PKs occurred in the majority of the plant associated genera, predominantly in Bacillus and Paenibacillus. Surprisingly, many genera from other environments contain no or few of such compounds indicating the role of these secondary metabolites in plant-associated niches.

Research paper thumbnail of Wake-up-call, a lin-52 paralogue, and Always early, a lin-9 homologue physically interact, but have opposing functions in regulating testis-specific gene expression

Developmental Biology, 2011

A conserved multi-subunit complex (MybMuvB, MMB), regulates transcriptional activity of many diff... more A conserved multi-subunit complex (MybMuvB, MMB), regulates transcriptional activity of many different target genes in Drosophila somatic cells. A paralogous complex, tMAC, controls expression of at least 1500 genes in the male germline, and is essential for sperm production. The roles of specific subunits of tMAC, MMB or orthologous complexes in regulating target gene expression are not understood. MMB and orthologous complexes have Lin-52 as a subunit, but Lin-52 did not co-purify with tMAC. We identified wake-up-call (wuc), a lin-52 paralogue, via a physical interaction with the tMAC lin-9-related subunit Aly, and find that Wuc co-localises with known tMAC subunits. We show that wuc, like aly, is required for spermatogenesis. However, despite phenotypic similarities, the role of wuc is very different from that of previously characterised tMAC mutants. Unlike aly, loss of wuc results in only relatively mild defects in testis-specific gene expression. Strikingly, wuc loss of function partially rescues expression of target genes in aly mutant testes. We propose that wuc represses testis-specific gene expression, that this repression is counteracted by aly, and that aly and a testis-specific TF II D complex work together to promote high transcriptional activity of spermiogenic genes specifically in primary spermatocytes.

Research paper thumbnail of The Draft Genome Sequence of Paenibacillus polymyxa Strain CCI-25 Encompasses High Potential for Secondary Metabolite Production

Genome announcements, 2016

We report here the draft genome sequence of Paenibacillus polymyxa strain CCI-25, which displays ... more We report here the draft genome sequence of Paenibacillus polymyxa strain CCI-25, which displays strong antifungal and antibacterial activities in vitro The genome encompasses nonribosomal peptide synthetases predicted to encode a tridecaptin, polymyxin, fusaricidin, an iturin-like synthetase, a lantibiotic similar to paenicidin A, as well as a type 1 polyketide synthase.

Research paper thumbnail of Surfactin variants mediate species-specific biofilm formation and root colonization inBacillus

Environmental Microbiology, 2016

Cyclic lipopeptides (cLP) and especially surfactins produced by Bacillus spp. trigger biofilm for... more Cyclic lipopeptides (cLP) and especially surfactins produced by Bacillus spp. trigger biofilm formation and root colonization and are crucial for biocontrol activity and systemic resistance in plants. Bacillus atrophaeus 176s isolated from the moss Tortella tortuosa produces the cLP fengycins, iturins and surfactins, possesses antifungal activities and can protect tomato, lettuce and sugar beet against Rhizoctonia solani infection. In B. atrophaeus we identified for the first time the variant surfactin C, which differs from surfactin A produced by B. subtilis and B. amyloliquefaciens by an isoleucine instead of a leucine at position 7 of the lipopeptide backbone. The analysis of the complete surfactin gene clusters revealed that the dissimilarity is encoded in the adenylation domain of srfC and show that surfactin variations are distributed in a species-specific manner in bacilli. We demonstrate that the surfactin A and C with subtle structural differences have varying signal strengths on biofilm formation and root colonization and act specifically on the respective producing strain. This became evident as biofilm formation and root colonization but not swarming motility in surfactin biosynthesis mutants was restored differentially in the presence of exogenously supplemented cognate and non-cognate surfactin variants.

Research paper thumbnail of Genome mining: Prediction of lipopeptides and polyketides from Bacillus and related Firmicutes

Computational and Structural Biotechnology Journal, 2015

Bacillus and related genera in the Bacillales within the Firmicutes harbor a variety of secondary... more Bacillus and related genera in the Bacillales within the Firmicutes harbor a variety of secondary metabolite gene clusters encoding polyketide synthases and non-ribosomal peptide synthetases responsible for remarkable diverse number of polyketides (PKs) and lipopeptides (LPs). These compounds may be utilized for medical and agricultural applications. Here, we summarize the knowledge on structural diversity and underlying gene clusters of LPs and PKs in the Bacillales. Moreover, we evaluate by using published prediction tools the potential metabolic capacity of these bacteria to produce type I PKs or LPs. The huge sequence repository of bacterial genomes and metagenomes provides the basis for such genome-mining to reveal the potential for novel structurally diverse secondary metabolites. The otherwise cumbersome task to isolate often unstable PKs and deduce their structure can be streamlined. Using web based prediction tools, we identified here several novel clusters of PKs and LPs from genomes deposited in the database. Our analysis suggests that a substantial fraction of predicted LPs and type I PKs are uncharacterized, and their functions remain to be studied. Known and predicted LPs and PKs occurred in the majority of the plant associated genera, predominantly in Bacillus and Paenibacillus. Surprisingly, many genera from other environments contain no or few of such compounds indicating the role of these secondary metabolites in plant-associated niches.

Research paper thumbnail of Wake-up-call, a lin-52 paralogue, and Always early, a lin-9 homologue physically interact, but have opposing functions in regulating testis-specific gene expression

Developmental Biology, 2011

A conserved multi-subunit complex (MybMuvB, MMB), regulates transcriptional activity of many diff... more A conserved multi-subunit complex (MybMuvB, MMB), regulates transcriptional activity of many different target genes in Drosophila somatic cells. A paralogous complex, tMAC, controls expression of at least 1500 genes in the male germline, and is essential for sperm production. The roles of specific subunits of tMAC, MMB or orthologous complexes in regulating target gene expression are not understood. MMB and orthologous complexes have Lin-52 as a subunit, but Lin-52 did not co-purify with tMAC. We identified wake-up-call (wuc), a lin-52 paralogue, via a physical interaction with the tMAC lin-9-related subunit Aly, and find that Wuc co-localises with known tMAC subunits. We show that wuc, like aly, is required for spermatogenesis. However, despite phenotypic similarities, the role of wuc is very different from that of previously characterised tMAC mutants. Unlike aly, loss of wuc results in only relatively mild defects in testis-specific gene expression. Strikingly, wuc loss of function partially rescues expression of target genes in aly mutant testes. We propose that wuc represses testis-specific gene expression, that this repression is counteracted by aly, and that aly and a testis-specific TF II D complex work together to promote high transcriptional activity of spermiogenic genes specifically in primary spermatocytes.

Research paper thumbnail of The Draft Genome Sequence of Paenibacillus polymyxa Strain CCI-25 Encompasses High Potential for Secondary Metabolite Production

Genome announcements, 2016

We report here the draft genome sequence of Paenibacillus polymyxa strain CCI-25, which displays ... more We report here the draft genome sequence of Paenibacillus polymyxa strain CCI-25, which displays strong antifungal and antibacterial activities in vitro The genome encompasses nonribosomal peptide synthetases predicted to encode a tridecaptin, polymyxin, fusaricidin, an iturin-like synthetase, a lantibiotic similar to paenicidin A, as well as a type 1 polyketide synthase.