Ecological and genetic analysis of copper and streptomycin resistance in Pseudomonas syringae pv. syringae

Strains of Pseudomonas syringae pv. syringae resistant to copper, streptomycin, or both compounds were recovered from symptomless and diseased tissue of four woody hosts in three nurseries in Oklahoma. In strains resistant to copper and streptomycin (Cu^r Sm^r), resistance to both compounds was cotransferred with a single plasmid which was either 68, 190, or 220 kilobase pairs (kb). All Cu^s Sm^r strains contained a 68-kb conjugative plasmid. Cu^r Sm^s, strains contained one plasmid which varied in size from 60 to 73 kb. All conjugative plasmids which transferred streptomycin resistance contained sequences homologous to the strA and strB Sm^r genes from the broad-host-range plasmid RSF1010. The Sm^r determinant was subsequently cloned from a 68-kb Cu^r Sm^r plasmid designated pPSR1. A restriction map detailing the organization of the homologous Sm^r genes from pPSR1 and RSF1010 and cloned Sm^r genes from P. syringae pv. papulans and Xanthomonas campestris pv. vesicatoria revealed the conservation of all sites studied. The Cu^r genes cloned from P. syringae pv. tomato PT23 and X. campestris pv. vesicatoria XV10 did not hybridize to the Cu^r plasmids identified in the present study, indicating that copper resistance in these P. syringae pv. syringae strains may be conferred by a distinct genetic determinant.Peer reviewedPlant Patholog

Transformation functions of soil color and climate

Measurements on modern soil color suggest well functional relationships between the soil formation process and the present climatic factors. The redness and yellowness of soil are chiefly caused by the contents of hematite and fullonite, and their correlations to climate are the best in humid regions in tropic and warm temperate regions. The lightness of soil mainly correlates to the organic accumulation, humification and carbonatization processes, and its correlation to climate can only be found in the humid-arid extratropical belt, The humidity and surface roughness of soil have so strong influence on soil color that there are great errors on the measurement of colorness in the field. The study on soil colors of typical loess sections shows that soil color can record the characteristics of Asia monsoon and the global climatic fluctuations well at millennial and ten-thousand-year scales. It can also indicate the pedogenesis and the climatic characteristics which magnetic susceptibility could not be reflected in humidity areas. Therefore, soil color can be used as a new climatic proxy which is easy and quick to measure, and will make an active influence on the study of global changes, geomorphology and Quaternary

Eustatic signals in deep-marine sedimentary sequences recovered at ODP Site 978, Alboran Basin, western Mediterranean Sea

A continuous section of Pliocene marine sediments was recovered at Ocean Drilling Program Site 978, located in the Alboran Sea between Spain and Morocco. Three Pliocene subunits have been defined at Site 978: the lowermost (Subunit IC, 129.2 m thick) is characterized by alternating beds of lighter, more calcareous, and darker less calcareous, claystone with bioturbated upper and lower contacts (Type 1 cycles); the middle (Subunit 1B, 67.1 m thick) is composed of relatively homogeneous nannofossil claystone; and the uppermost (Subunit IA, 211.6 m thick) contains abrupt-based darker, terrigenous layers interpreted as turbidites that are interstratified with lighter nannofossil claystone (Type 2 cycles). The rhythmically bedded light and dark layers in Subunit IC correlate with those in the Rosello Composite Section of Sicily, a global reference standard for the Pliocene time scale. These sedimentary cycles are products of variations in precession and resulting continental runoff. Missing cycles occur during eustatic highstands. The shift to more homogeneous sedimentation in Subunit IB is represented in similar-aged sequences throughout the Mediterranean which display evidence of submarine mass wasting. Mediterranean-wide slope degradation was likely a response to rapid sea-level change at approximately 3 Ma. This change in sedimentation style was accompanied by an upsection increase in sediment accumulation rates associated with turbidite influx in Subunit IA. Turbidite frequency throughout the Pliocene section can be linked to eustatic changes in sea level, with turbidite maxima corresponding with mid-sequence downlap surfaces and their associated condensed sections. © 2004, SEPM (Society for Sedimentary Geology)