Interaction of Linear Plasmid with Streptomyces rimosus Chromosome: Evidence for the Linearity of Chromosomal DNA

Recent studies imply that a linear chromosome may be characteristic of the Streptomyces genus. S. rimosus R6, the oxytetracy- cline (OTC) producer, carries a linear plasmid pPZGIOl that can interact with the bacterial chromosome to form integrants and plasmid-primes. Restriction analysis of one integrant (MV25) showed that pPZGIOl sequence had been integrated into the chromosome together with its linear end(s). Another strain (MV17) carried a linear plasmid of increased size of about 1 Mb (pPZG103). It was shown that OTC-genes were carried on the pPZG103, indicating that the plasmid was pPZGIOl\u27-OTC. Restriction mapping of pPZG103 demonstrated that one plasmid end was derived from the parental pPZGIOl while the other end was a linear chromosomal end. The linearity of S. rimosus R6 chromosomal DNA was further supported by the development of the chromosomal physical map

Persistence of the Chromosome End Regions at Low Copy Number in Mutant Strains of Streptomyces rimosus and Streptomyces lividans

Streptomycetes are important antibiotic producing bacteria that often exhibit genetic instability. One or both ends of the linear Streptomyces chromosome are lost spontaneously, resulting in viable mutant strains sometimes lacking hundreds of genes. We examined some strains of Streptomyces rimosus and Streptomyces lividans, which had been classified as »deletion mutants« and appeared to have lost chromosome end sequences. We discovered that the »deleted« sequences were still present in vegetative mycelium at a very low copy number so that they were normally not detected. The copy number in S. rimosus was estimated as 0.1–1.0 10–3/chromosome. Streptomyces spores contain the disappearing chromosome end sequences at a higher copy number than the vegetative mycelium, promoting their inheritance via spore preparations. This, in effect, represents a separation between germ line and deleted vegetative genomes, which has not been recognised before in Streptomyces, and has practical implications both for strain preservation and genetic studies

Od sekvencije DNA do kemijske strukture – pretraživanje mikrobnih genomskih i metagenomskih skupova podataka radi pronalaženja novih prirodnih spojeva

Rapid mining of large genomic and metagenomic data sets for modular polyketide synthases, non-ribosomal peptide synthetases and hybrid polyketide synthase/non-ribosomal peptide synthetase biosynthetic gene clusters has been achieved using the generic computer program packages ClustScan and CompGen. These program packages perform the annotation with the hierarchical structuring into polypeptides, modules and domains, as well as storage and graphical presentations of the data. This aims to achieve the most accurate predictions of the activities and specificities of catalytically active domains that can be made with present knowledge, leading to a prediction of the most likely chemical structures produced by these enzymes. The program packages also allow generation of novel clusters by homologous recombination of the annotated genes in silico. ClustScan and CompGen were used to construct a custom database of known compounds (CSDB) and of predicted entirely novel recombinant products (r-CSDB) that can be used for in silico screening with computer aided drug design technology. The use of these programs has been exemplified by analysing genomic sequences from terrestrial prokaryotes and eukaryotic microorganisms, a marine metagenomic data set and a newly discovered example of a \u27shared metabolic pathway\u27 in marine-microbial endosymbiosis.Brzo pretraživanje genomskih i metagenomskih skupova podataka, modularnih biosintetskih genskih nakupina poliketid sintaza i sintetaza neribosomalno sintetiziranih peptida, postignuto je primjenom generičkih računalnih programskih paketa ClustScan i CompGen. Ti programski paketi provode anotaciju hijerarhijskim strukturiranjem podataka na polipeptide, module i domene, te pohranu i grafičku prezentaciju tih podataka. Na temelju dosadašnjih spoznaja, nastoji se postići najtočnije moguće predviđanje aktivnosti i specifičnosti katalitički aktivnih domena, što vodi prema predviđanju najvjerojatnijih kemijskih struktura koje ti enzimi mogu sintetizirati. Programski paketi ClustScan i CompGen omogućuju generiranje novih genskih nakupina homolognom rekombinacijom anotiranih gena u uvjetima in silico, a upotrijebljeni su i za konstrukciju vlastitih baza podataka poznatih poliketidnih i peptidnih supstancija (CSDB) te potpuno novih poliketidnih i peptidnih supstancija produkata rekombinacije (r-CSDB). Ti će se produkti rekombinacije moći upotrijebiti za izbor supstancija s potencijalnom biološkom aktivnošću pomoću računalom vođenog dizajna lijekova u uvjetima in silico. Primjenjivost programskih paketa ClustScan i CompGen dokazana je u analizi genomskih sekvencija prokariotskih i eukariotskih mikroorganizama što žive u tlu, analizi metagenomske skupine podataka u uzorku iz morske vode, a i na nedavno opisanom primjeru \u27zajedničkog metaboličkoga puta\u27 u mikrobnog endosimbionta morske životinje

Clustering of protein domains for functional and evolutionary studies

Background: The number of protein family members defined by DNA sequencing is usually much larger than those characterised experimentally. This paper describes a method to divide protein families into subtypes purely on sequence criteria. Comparison with experimental data allows an independent test of the quality of the clustering. Results: An evolutionary split statistic is calculated for each column in a protein multiple sequence alignment; the statistic has a larger value when a column is better described by an evolutionary model that assumes clustering around two or more amino acids rather than a single amino acid. The user selects columns (typically the top ranked columns) to construct a motif. The motif is used to divide the family into subtypes using a stochastic optimization procedure related to the deterministic annealing EM algorithm (DAEM), which yields a specificity score showing how well each family member is assigned to a subtype. The clustering obtained is not strongly dependent on the number of amino acids chosen for the motif. The robustness of this method was demonstrated using six well characterized protein families: nucleotidyl cyclase, protein kinase, dehydrogenase, two polyketide synthase domains and small heat shock proteins. Phylogenetic trees did not allow accurate clustering for three of the six families. Conclusion: The method clustered the families into functional subtypes with an accuracy of 90 to 100%. False assignments usually had a low specificity score

From DNA sequences to chemical structures – methods for mining microbial genomic and metagenomic data sets for new natural products

Rapid mining of large genomic and metagenomic data sets for modular polyketide synthases, non-ribosomal peptide synthetases and hybrid polyketide synthase/non-ribosomal peptide synthetase biosynthetic gene clusters has been achieved using the generic computer program packages ClustScan and CompGen. These program packages perform the annotation with the hierarchical structuring into polypeptides, modules and domains, as well as storage and graphical presentations of the data. This aims to achieve the most accurate predictions of the activities and specificities of catalytically active domains that can be made with present knowledge, leading to a prediction of the most likely chemical structures produced by these enzymes. The program packages also allow generation of novel clusters by homologous recombination of the annotated genes in silico. ClustScan and CompGen were used to construct a custom database of known compounds (CSDB) and of predicted entirely novel recombinant products (r-CSDB) that can be used for in silico screening with computer-aided drug design technology. The use of these programs has been exemplified by analysing genomic sequences from terrestrial prokaryotes and eukaryotic microorganisms, a marine metagenomic data set and a newly discovered example of a 'shared metabolic pathway' in marine-microbial endosymbiosis

Global genome analysis of the shikimic acid pathway reveals greater gene loss in host-associated than in free-living bacteria

<p>Abstract</p> <p>Background</p> <p>A central tenet in biochemistry for over 50 years has held that microorganisms, plants and, more recently, certain apicomplexan parasites synthesize essential aromatic compounds via elaboration of a complete shikimic acid pathway, whereas metazoans lacking this pathway require a dietary source of these compounds. The large number of sequenced bacterial and archaean genomes now available for comparative genomic analyses allows the fundamentals of this contention to be tested in prokaryotes. Using Hidden Markov Model profiles (HMM profiles) to identify all known enzymes of the pathway, we report the presence of genes encoding shikimate pathway enzymes in the hypothetical proteomes constructed from the genomes of 488 sequenced prokaryotes.</p> <p>Results</p> <p>Amongst free-living prokaryotes most Bacteria possess, as expected, genes encoding a complete shikimic acid pathway, whereas of the culturable Archaea, only one was found to have a complete complement of recognisable enzymes in its predicted proteome. It may be that in the Archaea, the primary amino-acid sequences of enzymes of the pathway are highly divergent and so are not detected by HMM profiles. Alternatively, structurally unrelated (non-orthologous) proteins might be performing the same biochemical functions as those encoding recognized genes of the shikimate pathway. Most surprisingly, 30% of host-associated (mutualistic, commensal and pathogenic) bacteria likewise do not possess a complete shikimic acid pathway. Many of these microbes show some degree of genome reduction, suggesting that these host-associated bacteria might sequester essential aromatic compounds from a parasitised host, as a 'shared metabolic adaptation' in mutualistic symbiosis, or obtain them from other consorts having the complete biosynthetic pathway. The HMM results gave 84% agreement when compared against data in the highly curated BioCyc reference database of genomes and metabolic pathways.</p> <p>Conclusions</p> <p>These results challenge the conventional belief that the shikimic acid pathway is universal and essential in prokaryotes. The possibilities that non-orthologous enzymes catalyse reactions in this pathway (especially in the Archaea), or that there exist specific uptake mechanisms for the acquisition of shikimate intermediates or essential pathway products, warrant further examination to better understand the precise metabolic attributes of host-beneficial and pathogenic bacteria.</p

Novi pristup konstrukciji industrijskih mikroorganizama pomoću sintetičke biologije

The recent achievement of synthesising a functioning bacterial chromosome marks a coming of age for engineering living organisms. In the future this should allow the construction of novel organisms to help solve the problems facing the human race, including health care, food, energy and environmental protection. In this minireview, the current state of the field is described and the role of synthetic biology in biotechnology in the short and medium term is discussed. It is particularly aimed at the needs of food technologists, nutritionists and other biotechnologists, who might not be aware of the potential significance of synthetic biology to the research and development in their fields. The potential of synthetic biology to produce interesting new polyketide compounds is discussed in detail.Razvojem područja sinteze funkcionalnog bakterijskog kromosoma obilježen je početak novog doba genetičkog inženjerstva. Konstrukcijom novih organizama mogli bi se riješiti neki problemi vezani uz zdravstvo, proizvodnju hrane i energenata te zaštitu okoliša. U ovom su kratkom revijalnom prikazu opisana sadašnja dostignuća na području sintetičke biologije, a raspravlja se i o njezinoj ulozi u razvoju biotehnologije. Prikaz je posebno namijenjen prehrambenim tehnolozima, nutricionistima i ostalim biotehnolozima koji možda nisu svjesni značaja što bi sintetička biologija mogla imati za njihova istraživanja. Detaljno se raspravlja o mogućem utjecaju sintetičke biologije u formiranju potpuno novih poliketida, koji se mogu upotrijebiti za proizvodnju lijekova