Evolution of sensory complexity recorded in a myxobacterial genome.

Myxobacteria are single-celled, but social, eubacterial predators. Upon starvation they build multicellular fruiting bodies using a developmental program that progressively changes the pattern of cell movement and the repertoire of genes expressed. Development terminates with spore differentiation and is coordinated by both diffusible and cell-bound signals. The growth and development of Myxococcus xanthus is regulated by the integration of multiple signals from outside the cells with physiological signals from within. A collection of M. xanthus cells behaves, in many respects, like a multicellular organism. For these reasons M. xanthus offers unparalleled access to a regulatory network that controls development and that organizes cell movement on surfaces. The genome of M. xanthus is large (9.14 Mb), considerably larger than the other sequenced delta-proteobacteria. We suggest that gene duplication and divergence were major contributors to genomic expansion from its progenitor. More than 1,500 duplications specific to the myxobacterial lineage were identified, representing >15% of the total genes. Genes were not duplicated at random; rather, genes for cell-cell signaling, small molecule sensing, and integrative transcription control were amplified selectively. Families of genes encoding the production of secondary metabolites are overrepresented in the genome but may have been received by horizontal gene transfer and are likely to be important for predation.

Predicting holistic ratings of written performance assessments from analytic scoring.

The use of experts to judge performance assessments is desirable because ratings of performances, carried out by experts in the content domain of the examination, are often considered to be the "gold standard." However, one drawback of using experts to rate performances is the high cost involved. A more economic alternative for scoring performance assessments entails using analytic scoring, which typically involves assigning points to individual traits present in the performance, and summing to arrive at a single score. This strategy is less costly, but may lack the richness of holistic scoring. This study investigates the use of regression-based techniques to predict expert judgments on a written performance task from a combination of analytic scores. Potentially, this will result in scores that approximate the richness of holistic ratings while maintaining the cost-effectiveness of analytic scoring. Results show that a substantial proportion of variance in expert judgments can be explained by the analytic scores, but that decisions based on actual expert judgments and the predicted expert judgments were not sufficiently consistent to warrant the substitution of one score for the other.

Studying disruptive vocalization and contextual factors in the nursing home using computer-assisted real-time observation.

Disruptive vocalization (DV) is both a prevalent and disturbing problem in nursing homes. We developed a computer-assisted data collection system for real-time observation and recording of DV and various environmental contextual factors. Both frequency and duration of DV were recorded for 11 residents along with their location in the nursing home, their activity, environmental sound, the social environment, and whether or not the resident was physically restrained. The actual time of all events was also recorded. Measures of cognitive and ADL status were administered. The average occurrence of DV was 22 per hour and the average duration per occurrence was 26 seconds. The results show a significant upward linear trend in the occurrence of DV across the day. This is consistent with the "sundowning" hypothesis. A Cox Proportional Hazards Regression model indicates that another person present in the setting (p = .004) and resident presence at the nursing home hairdresser (p = .07) were associated with shorter duration episodes of DV. Correlational analyses indicate that both higher frequency and longer duration DV are related to greater cognitive impairment, and higher frequency DV is related to greater ADL impairment. We conclude that this computer-assisted real-time observational system is a useful and promising tool for studying disruptive behavior in its environmental context.

holE, the gene coding for the theta subunit of DNA polymerase III of Escherichia coli: characterization of a holE mutant and comparison with a dnaQ (epsilon-subunit) mutant.

DNA polymerase III holoenzyme is a multiprotein complex responsible for the bulk of chromosomal replication in Escherichia coli and Salmonella typhimurium. The catalytic core of the holoenzyme is an alpha epsilon theta heterotrimer that incorporates both a polymerase subunit (alpha; dnaE) and a proofreading subunit (epsilon; dnaQ). The role of theta is unknown. Here, we describe a null mutation of holE, the gene for theta. A strain carrying this mutation was fully viable and displayed no mutant phenotype. In contrast, a dnaQ null mutant exhibited poor growth, chronic SOS induction, and an elevated spontaneous mutation rate, like dnaQ null mutants of S. typhimurium described previously. The poor growth was suppressible by a mutation affecting alpha which was identical to a suppressor mutation identified in S. typhimurium. A double mutant null for both holE and dnaQ was indistinguishable from the dnaQ single mutant. These results show that the theta subunit is dispensable in both dnaQ+ and mutant dnaQ backgrounds, and that the phenotype of epsilon mutants cannot be explained on the basis of interference with theta function.

1992 Omnibus Survey. Portrait of the professions.

The portrait of our professions has changed in recent years, and the changes are quite positive. For example, the number of speech-language pathologists and audiologists who reported that they are unemployed and seeking employment has decreased while salaries reportedly continue to increase. These findings are especially encouraging given the current economic times. They represent a continuing demand for the valuable contributions that speech-language pathologists and audiologists can make in today's society. Caseload characteristics illustrate a different picture compared with data from previous years. Audiologists and speech-language pathologists both reported an increase in service provision to the birth-5 population. In addition, the severity of caseloads for speech-language pathologists has substantially decreased from that of previous years. The issues of support personnel, the AuD degree, and gender discrimination evoked expression of strong opinion. Based on the responses to these questions and the comments that accompanied them, it is apparent that there are many questions that need to be addressed before these issues reach consensus. We must continue to work together until we create a balanced picture. All in all, the portrait of the ASHA membership is both colorful and attractive--definitely suitable for framing. We should be proud of the progress that we have made over the years and of the image that we are creating for our professions. As we continue to take brush in hand, remember that each one of us can make a difference in the direction of our future. So splash on the colors and keep it bright!

Requirements for bypass of UV-induced lesions in single-stranded DNA of bacteriophage phi X174 in Salmonella typhimurium.

According to the current model for mutagenic bypass of UV-induced lesions, efficient bypass requires three proteins: activated RecA (RecA*) and either activated UmuD (UmuD') and UmuC or their plasmid-encoded analogues, MucA' and MucB. RecA* aids synthesis of UmuD' and UmuC (and MucA'/MucB) at two levels: by inactivation of the LexA transcriptional repressor of these genes and by cleavage of UmuD (and MucA) to produce the active fragments, UmuD' (MucA'). A third role for RecA is revealed when these two roles are otherwise satisfied in a suitably engineered strain. An often-suggested possible role for RecA in bypass is inhibition of editing by the epsilon subunit of DNA polymerase III. Here, by demonstrating that elimination of epsilon by deletion of its gene, dnaQ, does not relieve the requirement for the third function of RecA, we show that RecA must perform some function other than, or in addition to, inhibition of epsilon. We also show that elimination of epsilon does not relieve the requirement for either Muc protein. Moreover, we observed reactivation of irradiated phi X174 in unirradiated cells expressing MucA' and MucB. This finding makes it unlikely that the additional role of recA involves derepression of an unidentified gene or cleavage of an unidentified protein and makes it more likely that RecA participates directly in bypass.

Cloning and expression in Escherichia coli of the Alcaligenes eutrophus H16 poly-beta-hydroxybutyrate biosynthetic pathway.

The poly-beta-hydroxybutyrate (PHB) biosynthetic pathway from Alcaligenes eutrophus H16 has been cloned and expressed in Escherichia coli. Initially, an A. eutrophus H16 genomic library was constructed by using cosmid pVK102, and cosmid clones that encoded the PHB biosynthetic pathway were sought by assaying for the first enzyme of the pathway, beta-ketothiolase. Six enzyme-positive clones were identified. Three of these clones manifested acetoacetyl coenzyme A reductase activity, the second enzyme of the biosynthetic pathway, and accumulated PHB. PHB was produced in the cosmid clones at approximately 50% of the level found in A. eutrophus. One cosmid clone was subjected to subcloning experiments, and the PHB biosynthetic pathway was isolated on a 5.2-kilobase KpnI-EcoRI fragment. This fragment, when cloned into small multicopy vectors, can direct the synthesis of PHB in E. coli to levels approaching 80% of the bacterial cell dry weight.