University of Waterloo

About: University of Waterloo is a education organization based out in Waterloo, Ontario, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 36093 authors who have published 93906 publications receiving 2948139 citations. The organization is also known as: UW & uwaterloo.

Cadmium-tolerant plant growth-promoting bacteria associated with the roots of Indian mustard (Brassica juncea L. Czern.).

Abstract: Eleven cadmium-tolerant bacterial strains were isolated from the root zone of Indian mustard (Brassica juncea L. Czern.) seedlings grown in Cd-supplemented soils as well as sewage sludge and mining waste highly contaminated with Cd. The bacteria also showed increased tolerance to other metals including Zn, Cu, Ni and Co. The isolated strains included Variovorax paradoxus, Rhodococcus sp. and Flavobacterium sp., and were capable of stimulating root elongation of B. juncea seedlings either in the presence or absence of toxic Cd concentrations. Some of the strains produced indoles or siderophores, but none possessed C2H2-reduction activity. All the strains, except Flavobacterium sp. strain 5P-3, contained the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which hydrolyses ACC (the immediate precursor of plant hormone ethylene) to NH3 and a-ketobutyrate. V. paradoxus utilized ACC as a sole source of N or energy. A positive correlation between the in vitro ACC deaminase activity of the bacteria and their stimulating effect on root elongation suggested that utilization of ACC is an important bacterial trait determining root growth promotion. The isolated bacteria offer promise as inoculants to improve growth of the metal accumulating plant B. juncea in the presence of toxic Cd concentrations and for the development of plantinoculant systems useful for phytoremediation of polluted soils. q 2004 Elsevier Ltd. All rights reserved.

Generation of Multimillion-Sequence 16S rRNA Gene Libraries from Complex Microbial Communities by Assembling Paired-End Illumina Reads

Abstract: Microbial communities host unparalleled taxonomic diversity. Adequate characterization of environmental and host-associated samples remains a challenge for microbiologists, despite the advent of 16S rRNA gene sequencing. In order to increase the depth of sampling for diverse bacterial communities, we developed a method for sequencing and assembling millions of paired-end reads from the 16S rRNA gene (spanning the V3 region; ∼200 nucleotides) by using an Illumina genome analyzer. To confirm reproducibility and to identify a suitable computational pipeline for data analysis, sequence libraries were prepared in duplicate for both a defined mixture of DNAs from known cultured bacterial isolates (>1 million postassembly sequences) and an Arctic tundra soil sample (>6 million postassembly sequences). The Illumina 16S rRNA gene libraries represent a substantial increase in number of sequences over all extant next-generation sequencing approaches (e.g., 454 pyrosequencing), while the assembly of paired-end 125-base reads offers a methodological advantage by incorporating an initial quality control step for each 16S rRNA gene sequence. This method incorporates indexed primers to enable the characterization of multiple microbial communities in a single flow cell lane, may be modified readily to target other variable regions or genes, and demonstrates unprecedented and economical access to DNAs from organisms that exist at low relative abundances.

A device for measuring seepage flux in lakes and estuaries1

Abstract: Seepage flux can be measured and samples of groundwater flowing into lakes and estuaries collected by enclosing an area of bottom with a cylinder vented to a plastic bag. The method has the advantage of not requiring measurements of permeability of bottom sediments. Seepage velocities from −0.1–2.58 µm s−1 were measured in Minnesota and Wisconsin lakes and in Nova Scotia and North Carolina estuaries. Where seepage inflow was rapid (0.4–0.8 s−1), water collected with the seepage meter was chemically similar to water from wells on the same flow path, and the distribution and chemistry of the seepage concurred with a theoretical flow net. The rate and direction of seepage flux were correlated with water surface elevation during a tidal cycle.