The sulfonium ion linkage in myeloperoxidase. Direct spectroscopic detection by isotopic labeling and effect of mutation.

The heme group of myeloperoxidase is covalently linked via two ester bonds to the protein and a unique sulfonium ion linkage involving Met(243). Mutation of Met(243) into Thr, Gln, and Val, which are the corresponding residues of eosinophil peroxidase, lactoperoxidase, and thyroid peroxidase, respectively, and into Cys was performed. The Soret band in the optical absorbance spectrum in the oxidized mutants is now found at approximately 411 nm. Both the pyridine hemochrome spectra and resonance Raman spectra of the mutants are affected by the mutation. In the Met(243) mutants the affinity for chloride has decreased 100-fold. All mutants have lost their chlorination activity, except for the M243T mutant, which still has 15% activity left. By Fourier transform infared difference spectroscopy it was possible to specifically detect the (13)CD(3)-labeled methionyl sulfonium ion linkage. We conclude that the sulfonium ion linkage serves two roles. First, it serves as an electron-withdrawing substituent via its positive charge, and, second, together with its neighboring residue Glu(242), it appears to be responsible for the lower symmetry of the heme group and distortion from the planar conformation normally seen in heme-containing proteins.     

An evolutionary rearrangement of the Xp11.3-11.23 region in 3p21.3, a region frequently deleted in a variety of cancers.

In searching for a tumor suppressor gene in the 3p21.3 region, we isolated two genes, RBM5 and RBM6. Sequence analysis indicated that these genes share similarity. RBM5 and-to a lesser extent-RBM6 also have similarity to DXS8237E at Xp11.3-11.23, which maps less than 20 kb upstream of UBE1. A homologue of UBE1, UBE1L, is located at 3p21. 3. FISH analysis showed that the distance between UBE1L and RBM5 in 3p21.3 is about 265 kb. DXS8237E and UBE1 on the X chromosome have the same orientation, whereas on chromosome 3 the orientation of RBM5 and that of RBM6 are opposite to the orientation of UBE1L. Presumably, part of the Xp11.3-11.23 region has duplicated to chromosome 3. Part of this region on chromosome 3 may subsequently have duplicated again within the same chromosomal region. Inversion at some stage of the evolution of the human genome would explain the change in orientation of the genes on chromosome 3 compared with that of the genes on the X chromosome.     

Soil and plant factors driving the community of soil-borne microorganisms across chronosequences of secondary succession of chalk grasslands with a neutral pH

Although soil pH has been shown to be an important factor driving microbial communities, relatively little is known about the other potentially important factors that shape soil-borne microbial community structure. This study examined plant and microbial communities across a series of neutral pH fields (pH=7.0-7.5) representing a chronosequence of secondary succession after former arable fields were taken out of production. These fields ranged from 17 to >66 years since the time of abandonment, and an adjacent arable field was included as a reference. Hierarchical clustering analysis, nonmetric multidimensional scaling and analysis of similarity of 52 different plant species showed that the plant community composition was significantly different in the different chronosequences, and that plant species richness and diversity increased with time since abandonment. The microbial community structure, as analyzed by phylogenetic microarrays (PhyloChips), was significantly different in arable field and the early succession stage, but no distinct microbial communities were observed for the intermediate and the late succession stages. The most determinant factors in shaping the soil-borne microbial communities were phosphorous and NH(4)(+). Plant community composition and diversity did not have a significant effect on the belowground microbial community structure or diversity.     

Role of Leuconostoc mesenteroides in Leavening the Batter of Idli, a Fermented Food of India

The fermentation of the batter of idli, a fermented food of India, was studied. The microorganisms responsible for the characteristic changes in the batter were isolated and identified. Although there is a sequential change in the bacterial flora, the predominant microorganism responsible for souring, as well as for gas production, was found to be Leuconostoc mesenteroides. In the later stages of fermentation, growth of Streptococcus faecalis and, still later, of Pediococcus cerevisiae becomes significant. The fermentation of idli demonstrates a leavening action caused by the activity of the heterofermentative lactic acid bacterium, L. mesenteroides. As far as is known, this is the first record of a leavening action produced exclusively by the activity of a lactic acid bacterium.     

Metabolic Activity and Population Dynamics of Rhizobia Introduced into Unamended and Bentonite-Amended Loamy Sand

Respiration measurements showed that the cumulative amount of CO₂ respired by rhizobia introduced into sterile bentonite-amended loamy sand was significantly higher than it was in unamended loamy sand. The maintenance respiration of rhizobial cells was not influenced by the presence of bentonite clay. Carbon was used more efficiently during growth in bentonite-amended than in unamended loamy sand. The presence of bentonite clay increased the growth rate of rhizobia introduced into sterile soil. Survival studies performed in nonsterile bentonite-amended loamy sand showed that the use of high (10¹⁰ cells per g of dry soil) rather than lower (10⁴ to 10⁷ cells per g of dry soil) inoculum densities increased the final survival levels of introduced rhizobia. In unamended loamy sand, the application of 10¹⁰ or 10⁷ cells per g of dry soil resulted in similar final survival levels. Pore shape and the continuity of the water-filled pore system were suggested to largely determine the colonization rate of protective microhabitats.     

Investigations on the sheathed bacteriumHaliscomenobacter hydrossis gen.n., sp.n., isolated from activated sludge

The morphological and physiological properties of a recently isolated, thin, sheathed bacterium are described. The observations demonstrate that this bacterium differs from the known sheathed microorganisms in many characteristics. The following nomenclature is therefore proposed:Haliscomenobacter hydrossis gen.n. sp.n. The growth of this bacterium in activated sludge is discussed.     

Foetal and adult cardiomyocyte progenitor cells have different developmental potential

In the past years, cardiovascular progenitor cells have been isolated from the human heart and characterized. Up to date, no studies have been reported in which the developmental potential of foetal and adult cardiovascular progenitors was tested simultaneously. However, intrinsic differences will likely affect interpretations regarding progenitor cell potential and application for regenerative medicine. Here we report a direct comparison between human foetal and adult heart‐derived cardiomyocyte progenitor cells (CMPCs). We show that foetal and adult CMPCs have distinct preferences to differentiate into mesodermal lineages. Under pro‐angiogenic conditions, foetal CMPCs form more endothelial but less smooth muscle cells than adult CMPCs. Foetal CMPCs can also develop towards adipocytes, whereas neither foetal nor adult CMPCs show significant osteogenic differentiation. Interestingly, although both cell types differentiate into heart muscle cells, adult CMPCs give rise to electrophysiologically more mature cardiomyocytes than foetal CMPCs. Taken together, foetal CMPCs are suitable for molecular cell biology and developmental studies. The potential of adult CMPCs to form mature cardiomyocytes and smooth muscle cells may be essential for cardiac repair after transplantation into the injured heart.