Bilateral symmetry of linear streptomycete chromosomes

Here, we characterize an uncommon set of telomeres from Streptomyces rimosus ATCC 10970, the parental strain of a lineage of one of the earliest-discovered antibiotic producers. Following the closure of its genome sequence, we compared unusual telomeres from this organism with the other five classes of replicon ends found amongst streptomycetes. Closed replicons of streptomycete chromosomes were organized with respect to their phylogeny and physical orientation, which demonstrated that different telomeres were not associated with particular clades and are likely shared amongst different strains by plasmid-driven horizontal gene transfer. Furthermore, we identified a ~50 kb origin island with conserved synteny that is located at the core of all streptomycete chromosomes and forms an axis around which symmetrical chromosome inversions can take place. Despite this chromosomal bilateral symmetry, a bias in parS sites to the right of oriC is maintained across the family Streptomycetaceae and suggests that the formation of ParB/parS nucleoprotein complexes on the right replichore is a conserved feature in streptomycetes. Consequently, our studies reveal novel features of linear bacterial replicons that, through their manipulation, may lead to improvements in growth and productivity of this important industrial group of bacteria

Inactivation of Streptomyces phage ɸC31 by 405 nm light : requirement for exogenous photosensitizers?

Exposure to narrowband violet-blue light around 405 nm wavelength can induce lethal oxidative damage to bacteria and fungi, however effects on viruses are unknown. As photosensitive porphyrin molecules are involved in the microbicidal inactivation mechanism, and since porphyrins are absent in viruses, then any damaging effects of 405 nm light on viruses might appear unlikely. This study used the bacteriophage ɸC31, as a surrogate for non-enveloped double-stranded DNA viruses, to establish whether 405 nm light can induce virucidal effects. Exposure of ɸC31 suspended in minimal media, nutrient-rich media, and porphyrin solution, demonstrated differing sensitivity of the phage. Significant reductions in phage titre occurred when exposed in nutrient-rich media, with ~3, 5 and 7-log10 reductions achieved after exposure to doses of 0.3, 0.5 and 1.4 kJ/cm2, respectively. When suspended in minimal media a 0.3 log10 reduction (P=0.012) occurred after exposure to 306 J/cm2: much lower than the 2.7 and >2.5 log10 reductions achieved with the same dose in nutrient-rich, and porphyrin-supplemented media, suggesting inactivation is accelerated by the photo-activation of light-sensitive components in the media. This study provides the first evidence of the interaction of narrowband 405 nm light with viruses, and demonstrates that viral susceptibility to 405 nm light can be significantly enhanced by involvement of exogenous photosensitive components. The reduced susceptibility of viruses in minimal media, compared to that of other microorganisms, provides further evidence that the antimicrobial action of 405 nm light is predominantly due to the photo-excitation of endogenous photosensitive molecules such as porphyrins within susceptible microorganisms

Differential transcription of expanded gene families in central carbon metabolism of Streptomyces coelicolor A3(2)

Background: Streptomycete bacteria are prolific producers of specialised metabolites, many of which have clinically relevant bioactivity. A striking feature of their genomes is the expansion of gene families that encode the same enzymatic function. Genes that undergo expansion events, either by horizontal gene transfer or duplication, can have a range of fates: genes can be lost, or they can undergo neo-functionalisation or sub-functionalisation. To test whether expanded gene families in Streptomyces exhibit differential expression, an RNA-Seq approach was used to examine cultures of wild-type Streptomyces coelicolor grown with either glucose or tween as the sole carbon source. Results: RNA-Seq analysis showed that two-thirds of genes within expanded gene families show transcriptional differences when strains were grown on tween compared to glucose. In addition, expression of specialised metabolite gene clusters (actinorhodin, isorenieratane, coelichelin and a cryptic NRPS) was also influenced by carbon source. Conclusions: Expression of genes encoding the same enzymatic function had transcriptional differences when grown on different carbon sources. This transcriptional divergence enables partitioning to function under different physiological conditions. These approaches can inform metabolic engineering of industrial Streptomyces strains and may help develop cultivation conditions to activate the so-called silent biosynthetic gene clusters

In-vivo antimalarial activity of the endophytic actinobacterium, Streptomyces SUK 10

Endophytic bacteria, such as Streptomyces, have the potential to act as a source for novel bioactive molecules with medicinal properties. The present study was aimed at assessing the antimalarial activity of crude extract isolated from various strains of actinobacteria living endophytically in some Malaysian medicinal plants. Using the four day suppression test method on male ICR strain mice, compounds produced from three strains of Streptomyces (SUK8, SUK10, and SUK27) were tested in vivo against Plasmodium berghei PZZ1/100 in an antimalarial screen using crude extracts at four different concentrations. One of these extracts, isolated from Streptomyces SUK10 obtained from the bark of Shorea ovalis tree, showed inhibition of the test organism and was further tested against P. berghei-infected mice for antimalarial activity at different concentrations. There was a positive relationship between the survival of the infected mouse group treated with 50 μg/kg body weight (bw) of ethyl acetate-SUK10 crude extract and the ability to inhibit the parasites growth. The parasite inhibition percentage for this group showed that 50% of the mice survived for more than 90 days after infection with the parasite. The nucleotide sequence and phylogenetic tree suggested that Streptomyces SUK10 may constitute a new species within the Streptomyces genus. As part of the drug discovery process, these promising finding may contribute to the medicinal and pharmaceutical field for malarial treatment

Adaptation to endophytic lifestyle through genome reduction by Kitasatospora sp. SUK42

Endophytic actinobacteria offer great potential as a source of novel bioactive compounds. In order to investigate the potential for the production of secondary metabolites by endophytes, we recovered a filamentous microorgansism from the tree Antidesma neurocarpum Miq. After phenotypic analysis and whole genome sequencing we demonstrated that this organism, SUK42 was a member of the actinobacterial genus Kitasatospora. This strain has a small genome in comparison with other type strains of this genus and has lost metabolic pathways associated with Stress Response, Nitrogen Metabolism and Secondary Metabolism. Despite this SUK42 can grow well in a laboratory environment and encodes a core genome that is consistent with other members of the genus. Finally, in contrast to other members of Kitasatospora, SUK42 encodes saccharide secondary metabolite biosynthetic gene clusters, one of which with similarity to the acarviostatin cluster, the product of which displays α-amylase inhibitory activity. As extracts of the host plant demonstrate this inhibitory activity, it suggests that the potential medicinal properties of A. neurocarpum Miq might be provided by the endophytic partner and illustrate the potential for exploitation of endophytes for clinical or industrial uses

Estimation of ultrasonic attenuation and mean backscatterer size via digital signal processing

The backscattered rf signals from the lungs of fetal sheep during their last trimester of development were digitized and processed in an attempt to correlate ultrasonic parameters with measured functional parameters related to lung maturation. The broad-band, post-TGC, rf signal of a commercial B-mode ultrasonic scanner was digitized at a sampling rate of 25 MHz. Sorting excluded data from regions of rib shadowing and other nonlung structures from analysis. The sorted data were used to estimate the slope of the ultrasonic attenuation coefficient with respect to frequency via linear regression on the average difference of the logarithm of power spectra from separated data segments. The power spectra were also corrected for attenuation, averaged and used to compute the power cepstrum of the backscattered signal which can be related to mean backscatterer radius. Results are presented for eight fetal sheep.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24941/1/0000368.pd

Construction of a new class of tetracycline lead structures with potent antibacterial activity through biosynthetic engineering

Antimicrobial resistance and the shortage of novel antibiotics have led to an urgent need for new antibacterial drug leads. Several existing natural product scaffolds (including chelocardins) have not been developed because their suboptimal pharmacological properties could not be addressed at the time. It is demonstrated here that reviving such compounds through the application of biosynthetic engineering can deliver novel drug candidates. Through a rational approach, the carboxamido moiety of tetracyclines (an important structural feature for their bioactivity) was introduced into the chelocardins, which are atypical tetracyclines with an unknown mode of action. A broad-spectrum antibiotic lead was generated with significantly improved activity, including against all Gram-negative pathogens of the ESKAPE panel. Since the lead structure is also amenable to further chemical modification, it is a platform for further development through medicinal chemistry and genetic engineering

Gancidin W, a potential low toxicity antimalarial agent isolated from an Endophytic Streptomyces SUK10

As it resisted against nearly all current drugs, malaria was reported remained as the most threatening human parasitic disease. In line with this, endophytic Streptomyces are potential sources for novel bioactive molecules. In this study, prolyl-leucyl-diketopiperazine (C11H18N2O2) or Gancidin W (GW) was successfully isolated from Streptomyces SUK10 that inhabited in the bark of Shorea ovalis. Using four days suppressive test (4DST), this compound was in-vivo tested against Plasmodium berghei NK65. At 6.25 and 3.125 µg kg-1 body weight (bw), there was a very significant relationship of the ability to inhibit the growth of P. berghei NK65 when GW exhibited an inhibition rate of nearly 80% on male ICR strain mice. Comparing GW with dH2O diluted quinine hydrochloride and 0.9% normal saline as positive and negative controls respectively, 50% of the mice group treated with 3.125 µg kg-1 bw was managed to survive more than eight months post-infection exposure where this survival ranged was exceeded half of the normal mice’s life span period. As in-vivo toxicity assessment towards selected vital organs and blood enzymes were also investigated, the ALT and AST enzymes level was slightly higher but there was no abnormalities and injuries were found on the tested organs of the mice group treated with GW at this concentration. These findings indicated that GW isolated from Streptomyces SUK10 exhibited very low toxicity and is a good candidate as a potential antimalarial agent

Endophytic Streptomyces SUK10: its molecular characteristic and bioactivity against malaria parasite

It has been known that Streptomyces is the mains source for antibiotics. The present study found that the crude extract obtained from Streptomyces SUK10 living endophytically in Shorea ovalis tree has antimalarial activity against Plasmodium berghei strain PZZ1/100. Using validated surface sterilization and isolation method, Streptomyces SUK10 was isolated from the bark of Shorea ovalis by and cultured on the isolation agar. With spiral spore chain, microscopically, this strain has substrate mycelium in brownish yellow and aerial mycelium in whitish grey, other than yellow dissolved pigment. As showed in early molecular tests, the 23S rRNA sequence of Streptomyces SUK10 was 96% identical to Streptomyces hygroscopicus, the outstanding producer of Hygromycin B antibiotic. In early phase of antimalarial screening, the secondary metabolites from three different strains of endophytic Streptomyces isolated from three different trees were in-vivo tested on the mice ICR strain against P. berghei strain PZZ1/100. These were done by implementing the four days (4D) suppression test using their own ethyl acetate-crude extract at four different concentrations: 50, 100, 200 and 400 µg/kg body weight (bw). Upon obtaining significant results (p ≤ 0.05), ethyl acetate-SUK10 crude extract were screened for fully anti-malarial activity at five different narrower concentration range 5, 10, 50, 100 and 200 µg/kg bw. There was a positive relationship between the survival of the infected mice group treated with 50 µg/kg body weight of ethyl acetate-SUK10 crude extract and its ability to inhibit the parasites growth. Considering quinine hydrochloride at 10 mg/kg bw and 0.9% normal saline as positive and negative control respectively, the parasite inhibition percentage for this group at certain concentration showed more than 70% and 50% of this mice members (n=3) were also able to survive more than 90 days after the infection with the parasite. Nevertheless, Indole-3-lactic acid (C11H11NO3) was isolated from the anti-trypanosomal active fraction while Gancidin W or Maculosin 6 (L-leucyl-L-prolyl lactam, C11H18N2O2) was the major compound found from SUK 10 crude extract. Gancidin W has been previously reported to be anti-parasitic which we are still yet to be tested for anti-malarial activity and its cytotoxicity. These promising findings contribute to the medicinal and pharmaceutical field for future antimalarial treatment

Voting Technology, Vote-by-Mail, and Residual Votes in California, 1990-2010

This paper examines how the growth in vote-by-mail and changes in voting technologies led to changes in the residual vote rate in California from 1990 to 2010. We find that in California’s presidential elections, counties that abandoned punch cards in favor of optical scanning enjoyed a significant improvement in the residual vote rate. However, these findings do not always translate to other races. For instance, find that the InkaVote system in Los Angeles has been a mixed success, performing very well in presidential and gubernatorial races, fairly well for ballot propositions, and poorly in Senate races. We also conduct the first analysis of the effects of the rise of vote-by-mail on residual votes. Regardless of the race, increased use of the mails to cast ballots is robustly associated with a rise in the residual vote rate. The effect is so strong that the rise of voting by mail in California has mostly wiped out all the reductions in residual votes that were due to improved voting technologies since the early 1990s