Genome sequence and characterization of the bcs clusters for the production of nanocellulose from the low pH resistant strain Komagataeibacter medellinensis ID13488

Komagataeibacter medellinensis ID13488 (formerly Gluconacetobacter medellinensis ID13488) is able to produce crystalline bacterial cellulose (BC) under high acidic growth conditions. These abilities make this strain desirable for industrial BC production from acidic residues (e.g. wastes generated from cider production). To explore the molecular bases of the BC biosynthesis in this bacterium, the genome has been sequenced revealing a sequence of 3.4 Mb containing three putative plasmids of 38.1 kb (pKM01), 4.3 kb (pKM02) and 3.3 Kb (pKM03). Genome comparison analyses of K. medellinensis ID13488 with other cellulose-producing related strains resulted in the identification of the bcs genes involved in the cellulose biosynthesis. Genes arrangement and composition of four bcs clusters (bcs1, bcs2, bcs3 and bcs4) was studied by RT-PCR, and their organization in four operons transcribed as four independent polycistronic mRNAs was determined. qRT-PCR experiments demonstrated that mostly bcs1 and bcs4 are expressed under BC production conditions, suggesting that these operons direct the synthesis of BC. Genomic differences with the close related strain K. medellinensis NBRC 3288 unable to produce BC were also described and discussed.     

Characterization of transport-mediated methotrexate resistance in human tumor cells with antibodies to the membrane carrier for methotrexate and tetrahydrofolate cofactors.

An earlier report (Matherly, L. H., Czajkowski, C. A., and Angeles, S. M. (1991) Cancer Res. 51, 3420-3426) described a K562 human erythroleukemia line (K562.4CF), characterized by an elevated uptake capacity for methotrexate (MTX) and 5-formyltetrahydrofolate, and the identification of a highly glycosylated membrane transporter (GP-MTX) by radioaffinity labeling with N-hydroxysuccinimide [3H] methotrexate. In the present study, radioaffinity-labeled GP-MTX from K562.4CF cells was isolated by Ricinus communis agglutinin I-agarose affinity chromatography, coupled with gel filtration and preparative electrophoresis. Antiserum to the purified, radio-labeled protein was raised in a rabbit and screened by immunoblot analysis of K562.4CF plasma membrane proteins or purified GP-MTX. The antiserum detected a broad GP-MTX band centered at 92 kDa on 7.5% gels. On 4-10% gels, the apparent molecular mass for GP-MTX shifted to 99 kDa. Antiserum specificity was established by quantitatively converting the immunoreactive glycoprotein in plasma membrane homogenates to its N- and O-deglycosylated forms with N- and O-glycanases, respectively. Whereas the methotrexate uptake capacity of K562.4CF cells was elevated 6.1-fold over parental cells, the GP-MTX content on immunoblots was increased approximately 3-fold. For two methotrexate-resistant K562 lines (33- and 70-fold), decreased drug uptake (28 and 18% of parental levels) closely correlated with their reduced GP-MTX contents. A GP-MTX isoform was also detected on immunoblots of membrane proteins from CCRF-CEM human lymphoblastic leukemia cells. With a transport-impaired CCRF-CEM line (13% of wild type uptake), an aberrant electrophoretic migration for GP-MTX was observed, establishing the presence of structural modifications in the transport protein. These structural differences were independent of carrier glycosylation since they were detected following the glycosidase treatments. These findings implicate important roles for distinct carrier-specific alterations in the expression of diminished drug transport in methotrexate-resistant human tumor cells.     

Aerobiology of Castanea pollen in Galicia

The concentration of airborne chestnut pollenhas been investigated at four monitoringstations situated in several cities in Galicia(NW Spain) during 1995–1998. Their pollenseason takes place from mid June to thebeginning of August. The annual total chestnutpollen shows differences between years in eachcity. Likewise there are significantdifferences between cities in each year.The pollen concentrations were closelycorrelated with meteorological parameters. Theyincreased with maximum temperatures and hoursof sunshine and they decreased with rainfalland relative humidity.The diurnal variations of pollen concentrationsshow different patterns in urban and ruralareas. Where the spore trap is surrounded byarboreal masses with chestnut as the dominanttree, the pattern shows two peaks, one in theevening (between seven and mid-night) andanother in the morning (between four and one inthe afternoon).