Growth-promoting effects of Bradyrhizobium soybean symbionts in black oats, white oats, and ryegrass

Although inoculating soybean with rhizobia for biological nitrogen fixation is a common practice in agriculture, rhizobia are also known to associate with grasses. In this study, we evaluate the potential utility of the rhizobial strains SEMIA 587 and 5019 (Bradyrhizobium elkanii), 5079 (Bradyrhizobium japonicum), and 5080 (Bradyrhizobium diazoefficiens), recommended for Brazilian soybean inoculation, in colonizing black oat plants and promoting growth in black and white oats, and ryegrass. Inoculation of white oats with SEMIA 587 increase the seed germination (SG) by 32.09%, whereas the SG of black oats inoculated with SEMIA 587 and 5019 increased by 40.38% and 37.85%, respectively. Similarly, inoculation of ryegrass with all strains increased SG values between 24.63 and 27.59%. In addition, white oats with SEMIA 587 and 5080 had root areas significantly superior to those in other treatments, whereas inoculation with SEMIA 5079 and 5080 resulted in the highest volume of roots. Likewise, SEMIA 5079 and 5080 significantly increased the length, volume, and area of black oats roots, whereas SEMIA 587 increased the volume, area, and dry mass of roots and shoot. Inoculation in ryegrass with SEMIA 587 significantly increased the root volume. Moreover, most strains transformed with gfp and gus were observed to colonize the roots of black oats. Collectively, the findings of this study indicate that rhizobial strains recommended for inoculation of soybean can also be used to promote the growth of the three assessed grass species, and are able to colonize the roots of black oats.

Expression and characterization of the 42 kDa chitinase of the biocontrol fungus Metarhizium anisopliae in Escherichia coli

Albeit Metarhizium anisopliae is the best-characterized entomopathogenic fungus, the role of some hydrolytic enzymes during host cuticle penetration has not yet been established. Three chitinase genes (chit1, chi2, chi3) from Metarhizium have already been isolated. To characterize the chitinase coded by the chit1 gene, we expressed the active protein (CHIT42) in Escherichia coli using a T7-based promoter expression vector. The recombinant protein, CHIT42, is active against glycol chitin and synthetic N-acetylglucosamine (GlcNAc) dimer and tetramer substrates. These activities suggest that the recombinant CHIT42 acts as an endochitinase.

Mutations affecting motifs of unknown function in the central domain of nitrogen regulatory protein C

The positive control function of the bacterial enhancer-binding protein NtrC resides in its central domain, which is highly conserved among activators of sigma54 holoenzyme. Previous studies of a small set of mutant forms specifically defective in transcriptional activation, called NtrC repressor [NtrC(Rep)] proteins, had enabled us to locate various functional determinants in the central domain. In this more comprehensive survey, the DNA encoding a major portion of the central domain was randomly mutagenized and mutated ntrC genes were introduced into the cell via multicopy expression plasmids. DNA sequencing of 95 isolates identified by a preliminary phenotypic screen revealed that the lesions in them caused 55 distinct single amino acid substitutions at 44 different positions. Assays of glnA transcription in vivo and in vitro yielded two conclusions. First, of the 41 mutant proteins that could be purified, 17 (1 known, 16 new) showed no detectable activity in either assay, thus qualifying them as true NtrC(Rep) proteins. These contained residue changes in six of the seven highly conserved regions in the central domain, including two never studied before. Second, some mutant proteins were inactive in vivo but were either marginally or fully active in vitro. Their surprising lack of activity in vivo may be accounted for by high levels of expression, which apparently decreased activation by these mutant proteins but not by wild-type NtrC (NtrCWT). Of particular interest were a subset of these proteins that exhibited greater transcriptional activation than NtrCWT at low concentrations. Their elevated activation capacities remain to be explained.

Use of severity-adjusted length of stay to modify physician practice patterns

OBJECTIVE

To compare inpatient length of stay among physicians by testing a new method for severity adjusting length of stay.

DESIGN

A retrospective validation study with prospective follow-up after an intervention.

SETTING

A 531-bed community teaching hospital.

PATIENTS

Three hundred randomly selected patients from the 30,861 patients discharged in 1990.

INTERVENTION

A physician with a significantly prolonged severity-adjusted length of stay was counseled and then monitored for three months.

RESULTS

The correlation between the number of comorbidities, complications, and manifestations of disease processes (CCMDPs) was R2 = 0.658, t = 23.96 (p = .001). One physician had an unusually high severity-adjusted length of stay, but lowered it after he was counseled and monitored for three months.

CONCLUSIONS

The number of CCMDPs recorded on the hospital discharge abstract can be used as a severity index to adjust a patient's length of stay for illness severity. Using linear regression analysis, a picture of the severity-adjusted length of stay can be derived for physicians. Through counseling and monitoring, individual physicians' lengths of stay patterns may be reduced.