Independent Evolution with the Gene Flux Originating from Multiple Xanthomonas Species Explains Genomic Heterogeneity in Xanthomonas perforans.

Xanthomonas perforans is the predominant pathogen responsible for bacterial leaf spot of tomato and X. euvesicatoria for that of pepper in the southeast United States. Previous studies have indicated significant changes in the X. perforans population collected from Florida tomato fields over the span of 2 decades, including a shift in race and diversification into three phylogenetic groups driven by genome-wide homologous-recombination events derived from X. euvesicatoria In our sampling of Xanthomonas strains associated with bacterial spot disease in Alabama, we were readily able to isolate X. perforans from symptomatic pepper plants grown in several Alabama counties, indicating a recent shift in the host range of the pathogen. To investigate the diversity of these pepper-pathogenic strains and their relation to populations associated with tomatoes grown in the southeast United States, we sequenced the genomes of eight X. perforans strains isolated from tomatoes and peppers grown in Alabama and compared them with previously published genome data available from GenBank. Surprisingly, reconstruction of the X. perforans core genome revealed the presence of two novel genetic groups in Alabama that each harbored a different transcription activation-like effector (TALE). While one TALE, AvrHah1, was associated with an emergent lineage pathogenic to both tomato and pepper, the other was identified as a new class within the AvrBs3 family, here designated PthXp1, and was associated with enhanced symptom development on tomato. Examination of patterns of homologous recombination across the larger X. euvesicatoria species complex revealed a dynamic pattern of gene flow, with multiple donors of Xanthomonas spp. associated with diverse hosts of isolation.IMPORTANCE Bacterial leaf spot of tomato and pepper is an endemic plant disease with a global distribution. In this study, we investigated the evolutionary processes leading to the emergence of novel X. perforans lineages identified in Alabama. While one lineage was isolated from symptomatic tomato and pepper plants, confirming the host range expansion of X. perforans, the other lineage was isolated from tomato and acquired a novel transcription activation-like effector, here designated PthXp1. Functional analysis of PthXp1 indicated that it does not induce Bs4-mediated resistance in tomato and contributes to virulence, providing an adaptive advantage to strains on tomato. Our findings also show that different phylogenetic groups of the pathogen have experienced independent recombination events originating from multiple Xanthomonas species. This suggests a continuous gene flux between related xanthomonads associated with diverse plant hosts that results in the emergence of novel pathogen lineages and associated phenotypes, including host range.

Man's hand in evolution.

In developmental terms, the human hand is at the same time both specialised and primitive. Its manipulative ability, though somewhat better than that of the apes and monkeys, has lost strength compared with hands of recently extinct species of Man, and shows some evolutionary characteristics seen in reptiles of 250 million years ago. Its evolution, as presently understood, is described.

Functional disability in the rheumatoid hand.

The investigation of sixty-one rheumatoid patients relates their hand function to measured hand deformity. Certain deformities are related to a reduction in function; others are not. The dominant hand, used more frequently, deteriorates more quickly than the non-dominant. The benefit on hand function of synovectomy is limited in duration and should be accompanied by some procedure to defer or correct deformity. Study of the metacarphophalangeal joints by radiography and at operation shows that degeneration starts where the metacarpal head first loses articulation with the base of the phalanx, and spreads out from there across the metacarpal head as deformity increases.

Enzyme activity in human scars, hypertrophic scars and keloids.

Biopsies from non-hypertrophic and hypertrophic scars and from normal skin have been studied histochemically for activities of nicotanamide adenine dinucleotide diaphorase, lactate dehydrogenase, acid phosphatase, beta-D glucuronidase and alkaline phosphatase. The activities of all enzymes studied except alkaline phosphatase were found to be increased in hypertrophic scars as compared with non-hypertrophic scars and normal skin.

A clinical evaluation of the air-fluidised bed in a general plastic surgery unit.

Over a period of seven months nine patients were nursed on an air-fluidised bed. Measurements showed that skin-bed interface pressures were significantly lower on this bed than on a conventional hospital bed, particularly over the areas of the highest pressure. Whilst the bed did not shorten the patients' hospital stay, it did simplify nursing and improve patient comfort, especially in burns cases. Perhaps even more important was the observation that with correct use of the bed, no new pressure sores developed and established sores did not become worse.