Construction and characterization of new cloning vectors derived from Streptomyces griseobrunneus plasmid pBT1 and containing amikacin and sulfomycin resistance genes

The control mechanisms of heart rate dynamics in a new heart rate nonlinear time series model

The control mechanisms and implications of heart rate variability (HRV) under the sympathetic (SNS) and parasympathetic nervous system (PNS) modulation remain poorly understood. Here, we establish the HR model/HRV responder using a nonlinear process derived from Newton's second law in stochastic self-restoring systems through dynamic analysis of physiological properties. We conduct model validation by testing, predictions, simulations, and sensitivity and time-scale analysis. We confirm that the outputs of the HRV responder can be accepted as the real data-generating process. Empirical studies show that the dynamic control mechanism of heart rate is a stable fixed point, rather than a strange attractor or transitions between a fixed point and a limit cycle; HR slope (amplitude) may depend on the ratio of cardiac disturbance or metabolic demand mean (standard deviation) to myocardial electrical resistance (PNS-SNS activity). For example, when metabolic demands remain unchanged, HR amplitude depends on PNS to SNS activity; when autonomic activity remains unchanged, HR amplitude during resting reflects basal metabolism. HR parameter alterations suggest that age-related decreased HRV, ultrareduced HRV in heart failure, and ultraelevated HRV in ST segment alterations refer to age-related decreased basal metabolism, impaired myocardial metabolism, and SNS hyperactivity triggered by myocardial ischemia, respectively.

CRISPR/dCas9-mediated inhibition of gene expression in Staphylococcus aureus

The understanding of the genetic mechanism of Staphylococcus aureus requires efficient tools, however, genetic manipulation in S. aureus is always laborious and time-consuming. Here we proposed a novel CRISPR/dCas9 interference method for the rapid knockdown of target genes. Furthermore, multiple genes can be repressed simultaneously by using this method.

An external substrate-free blue/white screening system in Escherichia coli

Since the lacZα-based blue/white screening system was introduced to molecular biology, several different visual reporter systems were developed and used for various purposes in Escherichia coli. A common limit to the existent visual reporter systems is that an extracellular chromogenic substrate has to be added for the visible pigment production. In this study, we developed a new blue/white screening system based on a non-ribosomal peptide synthetase encoded by idgS from Streptomyces and a phosphopantetheinyl transferase encoded by sfp from Bacillus. When IdgS is activated from an apo-form to a holo-form via a posttranslational modification catalyzed by Sfp, it can synthesize a blue pigment indigoidine using L-glutamine, the amino acid abundant in cells, as a substrate. The new blue/white screening system contains a recipient E. coli strain with an optimized idgS gene cassette and a cloning vector harboring an sfp gene with an in-frame insertion of a multiple cloning site close to its N-terminal. We demonstrated that the IdgS/Sfp-based blue/white screening system is a powerful alternative to the lacZα-based screening system, which does not require any external substrate addition.

Development of recombinant Streptomyces for biotechnological and environmental uses

Recombinant DNA techniques for manipulation of genes in Streptomyces are well developed, and currently there is a high level of activity among researchers interested in applying molecular cloning and protoplast fusion techniques to strain development within this commercially important group of bacteria. A number of efficient plasmid and phage vector systems are being used for the molecular cloning of genes, primarily those encoding antibiotic biosynthesis enzymes, but also for a variety of other bioactive proteins and enzymes of known or potential commercial value. In addition, cloning aimed at constructing specialized bioconversion strains for use in the production of chemicals from organic carbon substrates is underway in numerous laboratories. This review discusses the current status of research involving recombinant DNA technologies applied to biotechnological applications using Streptomyces. The topic of potential environmental uses of recombinant Streptomyces is also reviewed, as is the status of current research aimed at assessing the fate and effects of recombinant Streptomyces in the environment. Also summarized is recent research that has confirmed that genetic exchange occurs readily among Streptomyces in the soil environment and which has shown the potential for exchange between recombinant Streptomyces and native soil bacteria.

Blue/white screening of recombinant plasmids in Gram-positive bacteria by interruption of alkaline phosphatase gene (phoZ) expression

The process of screening bacterial transformants for recombinant plasmids is made more rapid and simple by the use of vectors with visually detectable reporter genes. In such systems, an alteration in colony phenotype occurs when a vector-borne indicator gene is interrupted with exogenous DNA. Although the lacZ system has been used extensively for this purpose in E. coli, analogous systems for use in Gram-positive bacteria remain uncommon. We have developed a Gram-positive cloning vector that utilizes the interruption of an alkaline phosphatase gene, phoZ, to identify recombinant plasmids. To facilitate introduction of foreign DNA, a multiple cloning site (MCS) was inserted distal to the region coding for the putative signal peptide of phoZ. Alkaline phosphatase expressed from the derivative phoZ gene (phoZMCS) retained activity similar to that of the native protein. The phoZMCS was transferred to pJS3, a well-characterized, high-copy number, and broad-host-range plasmid, to produce pDC123. In pDC123, phoZMCS was transcriptionally linked to the chloramphenicol acetyl transferase (cat) gene under the control of the constitutively expressed tetM and cat promoters that drive cat expression in pJS3. S. agalactiae (Group B streptococci, GBS), E. faecalis, S. pyogenes, S. gordonii, and E. coli containing pDC123 displayed a blue colonial phenotype on agar containing 5-bromo-4-chloro-3-indolyl phosphate (X-p), which was readily distinguished from that of colonies containing the parent plasmid pJS3. Introduction of foreign DNA into the MCS of phoZMCS produced a white colonial phenotype in E. coli and GBS on agar containing X-p and allowed discrimination between transformants containing recombinant plasmids versus those maintaining self-annealed or uncut vector. We have used pDC123 to subclone the cpsE gene from the plasmid pCER111, which carries a 9.0-kb fragment of the GBS capsular polysaccharide synthesis locus. The plasmid pDC123 containing cpsE was isolated by direct electroporation into GBS strain A909 with selection of transformants containing recombinant plasmids achieved by 'blue/white' screening, without the use of an intermediate host. This new cloning vector should improve the efficiency of performing recombinant DNA experiments in Gram-positive bacteria.

Replication of the Streptomyces plasmid pSN22 through single-stranded intermediates

The replication of the 11 kb conjugative multicopy Streptomyces plasmid pSN22 was analyzed. Mutation and complementation analyses indicated that the minimal region essential for plasmid replication was located on a 1.9 kb fragment of pSN22, containing a transacting element encoding a replication protein and a cis-acting sequence acting as a replication origin. Southern hybridization showed that minimal replicon plasmids accumulated much more single-stranded plasmid molecules than did wild-type pSN22. Only one strand was accumulated. A 500 bp fragment from the pSN22 transfer region was identified which reduced the relative amount of single-stranded DNA, when added in the native orientation to minimal replicon plasmids. This 500 bp DNA sequence may be an origin for second-strand synthesis. It had no effect on the efficiency of co-transformation, plasmid incompatibility, or stability. The results indicate that pSN22 replicates via single-stranded intermediates by a rolling circle mechanism.