High deleterious genomic mutation rate in stationary phase of Escherichia coli

In natural habitats, bacteria spend most of their time in some form of growth arrest. Little is known about deleterious mutations in such stages, and consequently there is limited understanding of what evolutionary events occur. In a deleterious mutation accumulation experiment in prolonged stationary phase of Escherichia coli, about 0.03 slightly deleterious mutations were observed per genome per day. This is over an order of magnitude higher than extrapolations from fast-growing cells, but in line with inferences from observations in adaptive stationary phase mutation experiments. These findings may affect understanding of bacterial evolution and the emergence of bacterial pathogenicity.     

Role of Hec1 in spindle checkpoint signaling and kinetochore recruitment of Mad1/Mad2

The spindle checkpoint delays sister chromatid separation until all chromosomes have undergone bipolar spindle attachment. Checkpoint failure may result in chromosome mis-segregation and may contribute to tumorigenesis. We showed that the human protein Hec1 was required for the recruitment of Mps1 kinase and Mad1/Mad2 complexes to kinetochores. Depletion of Hec1 impaired chromosome congression and caused persistent activation of the spindle checkpoint, indicating that high steady-state levels of Mad1/Mad2 complexes at kinetochores were not essential for checkpoint signaling. Simultaneous depletion of Hec1 and Mad2 caused catastrophic mitotic exit, making Hec1 an attractive target for the selective elimination of spindle checkpoint-deficient cells.     

Mineral nutrition and water use patterns of a maize/cowpea intercrop on a highly acidic soil of the tropic semiarid

Due to global warming, water is expected to become scarce especially in semiarid regions. Therefore, there is a need to increase the efficiency in water use by crops under rainfed agriculture. The effect of nutrient availability on the growth, production, root development, water relations and water use efficiency (WUE) by the intercrop maize/cowpea was investigated in 2 contrasting years (dry and wet) in the semiarid region of Brazil. The crops were grown on a strongly acidic, sandy soil with three treatments: (i) application of NPK fertilizers plus lime (NPK + lime), (ii) application of NPK fertilizers (NPK) and (ii) control (Contr.) in low and high input regimes. The soil water balance was calculated with the crop model EPICSEAR. Application of fertilizers and lime increased biomass production and grain yield of the intercrop up to 400% and 550%, respectively, and maize suffered more from the effects of low nutrient availability and soil acidity than cowpea. The root development of both crops was strongly improved by the application of NPK and lime and cowpea developed a deeper root system which enabled this crop to keep a higher transpiration rate in the dry year. As a consequence of the shallow root system, maize was prone to water stresses caused by the dry spells and its harvest index was reduced when dry spells occurred during flowering and grain filling.     

Biological evaluation of phytoplankton (Chlorella sp., Tetraselmis sp. and Isochrysis galbana) as food for milkfish (Chanos chanos) fry

Phytoplankton cultures of Chlorella sp., Tetraselmis sp. and Isochrysis galbana were used alone as feed to rear separate batches of newly caught milkfish (Chanos chanos) fry (about 21 days old). Ultrastructural studies of fry hepatocytes and pancreatic acinar cells indicated that they cannot directly utilize Chlorella, which has a rigid cell wall. The fry can directly utilize Tetraselmis and Isochrysis, but neither is nutritionally adequate for growth and survival if used as the only feed. Tetraselmis is nutritionally inferior to Isochrysis.