Estimations of Bacterial Growth Rates in Natural Waters

Specific growth rates as low as 0.005 hr⁻¹ (generation times of 20 to 200 hr) of aquatic bacteria in natural waters have been calculated from significant differences between dilution rates and washout rates in a chemostat. The measured growth rates were affected by the treatment of the water samples (type of sterilization) and by competition with the natural microflora for the unknown growth-limiting substrate.     

Accumulation of Hydroxycoumarins During Post-harvest Deterioration of Tuberous Roots of Cassava (Manihot esculenta Crantz)

The use of the root crop Cassava (Manihot esculenta Crantz)is constrained by its rapid deterioration after harvest. Chemicaland spectroscopic examination revealed the accumulation of fourhydroxycoumarins (esculin, esculetin, scopolin and scopoletin),compounds derived from the phenylpropanoid pathway, during thetime course of post-harvest deterioration. Fluorescence-microscopyrevealed their localization in the apoplast of the parenchyma.Scopoletin and scopolin showed the most dramatic increases inconcentration, peaking by day 2 after harvesting. A smallersecondary peak of scopoletin tended to be more pronounced incultivars showing lower susceptibility to deterioration. Evidencefor the metabolism of scopoletin to an insoluble coloured productby means of a peroxidase is presented. This product may be thecause of the discolouration of the vascular tissue during storage.Copyright 2000 Annals of Botany Company Cassava, hydroxycoumarins, Manihot esculenta, peroxidases, post-harvest physiological deterioration, wound response     

Immunological evidence for a ribulose bisphosphate carboxylase-like protein in the symbiotic dinoflagellate Symbiodinium sp.

Whereas previously there has been no convincing evidence for ribulose bisphosphate carboxylase in dinoflagellates, a strong and highly specific reaction was observed when antibodies to the denatured large subunit of the (silver beet) protein were used to probe Western blots of whole soluble fractions of various Symbiodinium isolates. No reaction was observed using extracts from Symbiodinium isolated from a host which had been maintained under low light intensity. The results imply extensive sequence homology between the large subunit of ribulose bisphosphate carboxylase and a dinoflagellate protein of M , approximately 35 000.     

In Vivo Transplantation of Neurosphere-Like Bodies Derived from the Human Postnatal and Adult Enteric Nervous System: A Pilot Study

Recent advances in the in vitro characterization of human adult enteric neural progenitor cells have opened new possibilities for cell-based therapies in gastrointestinal motility disorders. However, whether these cells are able to integrate within an in vivo gut environment is still unclear. In this study, we transplanted neural progenitor-containing neurosphere-like bodies (NLBs) in a mouse model of hypoganglionosis and analyzed cellular integration of NLB-derived cell types and functional improvement. NLBs were propagated from postnatal and adult human gut tissues. Cells were characterized by immunohistochemistry, quantitative PCR and subtelomere fluorescence in situ hybridization (FISH). For in vivo evaluation, the plexus of murine colon was damaged by the application of cationic surfactant benzalkonium chloride which was followed by the transplantation of NLBs in a fibrin matrix. After 4 weeks, grafted human cells were visualized by combined in situ hybridization (Alu) and immunohistochemistry (PGP9.5, GFAP, SMA). In addition, we determined nitric oxide synthase (NOS)-positive neurons and measured hypertrophic effects in the ENS and musculature. Contractility of treated guts was assessed in organ bath after electrical field stimulation. NLBs could be reproducibly generated without any signs of chromosomal alterations using subtelomere FISH. NLB-derived cells integrated within the host tissue and showed expected differentiated phenotypes i.e. enteric neurons, glia and smooth muscle-like cells following in vivo transplantation. Our data suggest biological effects of the transplanted NLB cells on tissue contractility, although robust statistical results could not be obtained due to the small sample size. Further, it is unclear, which of the NLB cell types including neural progenitors have direct restoring effects or, alternatively may act via ‘bystander’ mechanisms in vivo. Our findings provide further evidence that NLB transplantation can be considered as feasible tool to improve ENS function in a variety of gastrointestinal disorders.     

Spatio-Temporal Variability of Copepod Abundance along the 20°S Monitoring Transect in the Northern Benguela Upwelling System from 2005 to 2011

Long-term data sets are essential to understand climate-induced variability in marine ecosystems. This study provides the first comprehensive analysis of longer-term temporal and spatial variations in zooplankton abundance and copepod community structure in the northern Benguela upwelling system from 2005 to 2011. Samples were collected from the upper 200 m along a transect at 20°S perpendicular to the coast of Namibia to 70 nm offshore. Based on seasonal and interannual trends in surface temperature and salinity, three distinct time periods were discernible with stronger upwelling in spring and extensive warm-water intrusions in late summer, thus, high temperature amplitudes, in the years 2005/06 and 2010/11, and less intensive upwelling followed by weaker warm-water intrusions from 2008/09 to 2009/10. Zooplankton abundance reflected these changes with higher numbers in 2005/06 and 2010/11. In contrast, zooplankton density was lower in 2008/09 and 2009/10, when temperature gradients from spring to late summer were less pronounced. Spatially, copepod abundance tended to be highest between 30 and 60 nautical miles off the coast, coinciding with the shelf break and continental slope. The dominant larger calanoid copepods were Calanoides carinatus, Metridia lucens and Nannocalanus minor. On all three scales studied, i.e. spatially from the coast to offshore waters as well as temporally, both seasonally and interannually, maximum zooplankton abundance was not coupled to the coldest temperature regime, and hence strongest upwelling intensity. Pronounced temperature amplitudes, and therefore strong gradients within a year, were apparently important and resulted in higher zooplankton abundance.     

A Novel High-Resolution Single Locus Sequence Typing Scheme for Mixed Populations of Propionibacterium acnes In Vivo

The Gram-positive anaerobic bacterium Propionibacterium acnes is a prevalent member of the normal skin microbiota of human adults. In addition to its suspected role in acne vulgaris it is involved in a variety of opportunistic infections. Multi-locus sequence-typing (MLST) schemes identified distinct phylotypes associated with health and disease. Being based on 8 to 9 house-keeping genes these MLST schemes have a high discriminatory power, but their application is time- and cost-intensive. Here we describe a single-locus sequence typing (SLST) scheme for P. acnes. The target locus was identified with a genome mining approach that took advantage of the availability of representative genome sequences of all known phylotypes of P. acnes. We applied this SLST on a collection of 188 P. acnes strains and demonstrated a resolution comparable to that of existing MLST schemes. Phylogenetic analysis applied to the SLST locus resulted in clustering patterns identical to a reference tree based on core genome sequences. We further demonstrate that SLST can be applied to detect multiple phylotypes in complex microbial communities by a metagenomic pyrosequencing approach. The described SLST strategy may be applied to any bacterial species with a basically clonal population structure to achieve easy typing and mapping of multiple phylotypes in complex microbiotas. The P. acnes SLST database can be found at http://medbac.dk/slst/pacnes.     

Pyruvate Decarboxylase Catalysed Formation of Terpenoid α-hydroxy Ketones

Enzyme extracts of the wild type yeast Zygosaccharomyces bisporus were applied for the pyruvate decarboxylase catalysed condensation of pyruvate and (R)-(+)-and (S)-(?)-perillyl aldehyde, (±)-citronellal, neral, geranial or (R)-(?)-myrtenal to form novel α-hydroxy ketones. Best yields were obtained when the transformation medium contained 25% (v/v) of the cosolvent N,N-dimethylformamide. Conversion of (R)-(+)-perillyl aldehyde to (1R)-1-hydroxy-1-[(4’R)-4’-isopropenyl-1-cyclohexen-1-yl]-2-propanone proceeded highly stereospecifically (>99% de), whereas the stereoselectivity was somewhat less in the transformation of (S)-(?)-perillyl aldehyde (58% de) and (R)-(?)-myrtenal (92% de). All of the new compounds imparted characteristic odour impressions as determined by means of GC-olfactometry.