Binding of homologous polymerized deoxyribonucleic acid by Streptomyces griseus

Germaine, G. R. (University of Minnesota, Minneapolis), and D. L. Anderson. Binding of homologous polymerized deoxyribonucleic acid by Streptomyces griseus. J. Bacteriol. 92:662-667. 1966-An irreversible P(32) deoxyribonucleic acid (DNA) binding system is described for Streptomyces griseus S104. The 69% guanine plus cytosine (GC) S. griseus DNA was bound by late exponential -early stationary phase cultures. Simultaneous addition of deoxyribonuclease with the P(32)-DNA to maximally receptive cultures reduced the uptake by 98%. Saturation of the binding ability occurred after 20-min incubation of cells with P(32)-DNA. Preparative cesium chloride density gradient centrifugation of the P(32)-DNA revealed that 98% of the label banded in the position expected for S. griseus DNA. Sedimentation of the P(32)-DNA at both 23 and 37 mug/ml indicated a molecular weight of 10.8 million. Attempts to transform S. griseus S104 auxotrophs to prototrophy by use of immediate and delayed selective procedures were unsuccessful.     

The structure of cyanobacterial phycobilisomes: a model

Phycobilisomes, supramolecular complexes of water-soluble accessory pigments, serve as the major light-harvesting antennae in cyanobacteria and red algae. Regular arrays of these organelles are found on the surface of the thylakoid membranes of these organisms. In the present study, the hemi-discoidal phycobilisomes of several species of cyanobacteria were examined in thin sections of cells and by negative staining after isolation and fixation. Their fundamental structures were found to be the same. Isolated phycobilisomes possessed a triangular core assembled from three stacks of disc-shaped subunits. Each stack contained two discs which were 12 nm in diameter and 6–7 nm thick. Each of these discs was probably subdivided into halves 3–3.5 nm thick. Radiating from each of two sides of the triangular core were three rods 12 nm in diameter. Each rod consisted of stacks of 2 to 6 disc-shaped subunits 6 nm thick. These discs were subdivided into halves 3 nm thick.The average number of discs of 6 nm thickness forming the peripheral rods varied among the strains studied. For certain chromatically adapting strains, the average rod length was dependent upon the wavelength of light to which cells were exposed during growth. Analyses of phycobilisomes by spectroscopic techniques, polyacrylamide gel electrophoresis, and electron microscopy were compared. These analyses suggested that the triangular core was composed of allophycocyanin and that the peripheral rods contained phycocyanin and phycoerythrin (when present). A detailed model of the hemi-discoidal phycobilisome is proposed. This model can account for many aspects of phycobiliprotein assembly and energy transfer.Abbreviations PBS phycobilisome(s) - PBP phycobiliprotein(s) - AP allophycocyanin - PC phycocyanin - PE phycoerythrin - PEC phycoerythrocyanin - AP-B allophycocyanin B - C- cyanobacterial - R- rhodophytan - B- Bangiophycean - SDS sodium dodecyl sulfate - LPP Lyngbya-Plectonema-Phormidium group - Na-KPO₄ buffers NaH₂PO₄ titrated with a solution of KH₂PO₄ of equivalent molarity to a given pH     

Alginate beads as a storage, delivery and containment system for genetically modified PCB degrader and PCB biosensor derivatives of Pseudomonas fluorescens F113

Aims: Pseudomonas fluorescens F113Rifpcb is a genetically engineered rhizosphere bacterium with the potential to degrade polychlorinated biphenyls (PCBs). F113Rifpcbgfp and F113L::1180gfp are biosensor strains capable of detecting PCB bioavailability and biodegradation. The aim of this paper is to evaluate the use of alginate beads as a storage, delivery and containment system for use of these strains in PCB contaminated soils. Methods and Results: The survival and release of Ps. fluorescens F113Rifpcb from alginate beads were evaluated. Two Ps. fluorescens F113‐based biosensor strains were encapsulated, and their ability to detect 3‐chlorobenzoate (3‐CBA) and 3‐chlorobiphenyl (3‐CBP) degradation in soil was assessed. After 250 days of storage, 100% recovery of viable F113Rifpcb cells was possible. Amendments to the alginate formulation allowed for the timed release of the inoculant. Encapsulation of the F113Rifpcb cells provided a more targeted approach for the inoculation of plants and resulted in lower inoculum populations in the bulk soil, which may reduce the risk of unintentional spread of these genetically modified micro‐organisms in the environment. Encapsulation of the biosensor strains in alginate beads did not interfere with their ability to detect either 3‐CBA or 3‐CBP degradation. In fact, detection of 3‐CBP degradation was enhanced in encapsulated biosensors. Conclusions: Alginate beads are an effective storage and delivery system for PCB degrading inocula and biosensors. Significance and Impact of the Study: Pseudomonas fluorescens F113Rifpcb and the F113 derivative PCB biosensor strains have excellent potential for detecting and bioremediation of PCB contaminated soils. The alginate bead delivery system could facilitate the application of these strains as biosensors.     

MRI study of minor physical anomaly in childhood autism implicates aberrant neurodevelopment in infancy

Background

MPAs (minor physical anomalies) frequently occur in neurodevelopmental disorders because both face and brain are derived from neuroectoderm in the first trimester. Conventionally, MPAs are measured by evaluation of external appearance. Using MRI can help overcome inherent observer bias, facilitate multi-centre data acquisition, and explore how MPAs relate to brain dysmorphology in the same individual. Optical MPAs exhibit a tightly synchronized trajectory through fetal, postnatal and adult life. As head size enlarges with age, inter-orbital distance increases, and is mostly completed before age 3 years. We hypothesized that optical MPAs might afford a retrospective ‘window’ to early neurodevelopment; specifically, inter-orbital distance increase may represent a biomarker for early brain dysmaturation in autism.

Methods

We recruited 91 children aged 7–16; 36 with an autism spectrum disorder and 55 age- and gender-matched typically developing controls. All children had normal IQ. Inter-orbital distance was measured on T1-weighted MRI scans. This value was entered into a voxel-by-voxel linear regression analysis with grey matter segmented from a bimodal MRI data-set. Age and total brain tissue volume were entered as covariates.

Results

Intra-class coefficient for measurement of the inter-orbital distance was 0.95. Inter-orbital distance was significantly increased in the autism group (p = 0.03, 2-tailed). The autism group showed a significant relationship between inter-orbital distance grey matter volume of bilateral amygdalae extending to the unci and inferior temporal poles.

Conclusions

Greater inter-orbital distance in the autism group compared with healthy controls is consistent with infant head size expansion in autism. Inter-orbital distance positively correlated with volume of medial temporal lobe structures, suggesting a link to “social brain” dysmorphology in the autism group. We suggest these data support the role of optical MPAs as a “fossil record” of early aberrant neurodevelopment, and potential biomarker for brain dysmaturation in autism.     

Forest Restoration Treatment Effects on the Nesting Success of Western Bluebirds (Sialia mexicana)

We examined the effects of presettlement forest restoration treatments on the nesting success of Western Bluebirds in ponderosa pine forests of northwestern Arizona, U.S.A. From 1998 to 2001 we monitored 97 active Western Bluebird nests, 41 in current‐condition untreated forest and 56 in restoration‐treated forest. We found no effect of restoration treatments on clutch size and little effect on the number of nestlings per nest. However, in treated forest stands number of fledglings per nest averaged 1.6 times greater, and probability of a nest surviving to successfully fledge at least one young was up to 4.2 times greater than in untreated forest. Probability of a nest succeeding averaged 0.39 ± 0.11 (SE) and 0.75 ± 0.06 from 1999 to 2001 in untreated and treated forests, respectively. In addition, in treated forest, average number of nests infested with the blowfly parasite Protocalliphora sialia was up to 4.3 times greater, and number of parasites per fledgling was up to 10.7 times greater than in untreated forest. Overall, the data suggest that in treated forest Western Bluebirds have a higher probability of successfully fledging young, but they are at greater risk of parasitic infestations, of which the ultimate effects on post‐fledging survival are unknown.     

Associations of physical activity with gut microbiota in pre-adolescent children

[Purpose] To determine whether physical activity (PA), primarily the recommended 60 minutes of moderate-to-vigorous PA, is associated with gut bacterial microbiota in 10-year-old children.[Methods] The Block Physical Activity Screener, which provides minutes/day PA variables, was used to determine whether the child met the PA recommendations. 16S rRNA sequencing was performed on stool samples from the children to profile the composition of their gut bacterial microbiota. Differences in alpha diversity metrics (richness, Pielou’s evenness, and Faith’s phylogenetic diversity) by PA were determined using linear regression, whereas beta diversity (unweighted and weighted UniFrac) relationships were assessed using PERMANOVA. Taxon relative abundance differentials were determined using DESeq2.[Results] The analytic sample included 321 children with both PA and 16S rRNA sequencing data (mean age [SD] =10.2 [0.8] years; 54.2% male; 62.9% African American), where 189 (58.9%) met the PA recommendations. After adjusting for covariates, meeting the PA recommendations as well as minutes/day PA variables were not significantly associated with gut richness, evenness, or diversity (p ≥ 0.19). However, meeting the PA recommendations (weighted UniFrac R² = 0.014, p = 0.001) was significantly associated with distinct gut bacterial composition. These compositional differences were partly characterized by increased abundance of Megamonas and Anaerovorax as well as specific Christensenellaceae_R-7_group taxa in children with higher PA.[Conclusion] Children who met the recommendations of PA had altered gut microbiota compositions. Whether this translates to a reduced risk of obesity or associated metabolic diseases is still unclear.     

Determinism of bacterial metacommunity dynamics in the southern East China Sea varies depending on hydrography

Spatial variation of communities composition (metacommunities) results from multiple assembly mechanisms, including environmental filtering and dispersal; however, whether and why the relative importance of the assembly mechanisms in shaping bacterial metacommunity changes through time in marine pelagic systems remains poorly studied. Here, we applied the elements of metacommunity structure framework and the variation partitioning framework to examine whether temporal variation of hydrographic conditions influences bacterioplankton metacommunity dynamics in the southern East China Sea (ECS). The spatiotemporal variation of bacterial communities composition was revealed using 454 pyrosequencing of 16S rDNA. In addition to the whole bacterial community, we analyzed four dominant taxonomic groups (Cyanobacteria, Alphaproteobacteria, Gammaproteobacteria, and Actinobacteria) separately. Our analyses indicate that, considering the whole community level, the determinism of metacommunity structure varied among seasons. When the degree of connectivity was low (December), the metacommunity exhibited random distribution and was explained mainly by the environmental component. However, Clementsian metacommunity was found at intermediate connectivity (May), during which the environmental and spatial predictors were both significant. When connectivity was high (August), a random distribution pattern was found and no significant effect of environmental filtering or dispersal limitation was detected. Nevertheless, when considering different taxonomic groups, the differences in metacommunity dynamics among groups were found. Our results suggest that the driving forces of metacommunity dynamics varied depending on hydrography, as the degrees of environmental heterogeneity and connectivity among habitat patches were determined by circulation pattern. Moreover, mechanisms varied among different taxonomic groups, suggesting that differential dispersal capacity among taxonomic groups should be integrated into community assembly studies.