A defined template mixture of seven closely related 16S-rDNA clones was used in a PCR-cloning experiment to assess and track sources of artifactual sequence variation in 16S rDNA clone libraries. At least 14% of the recovered clones contained aberrations. Artifact sources were polymerase errors, a mutational hot spot, and cloning of heteroduplexes and chimeras. These data may partially explain the high degree of microheterogeneity typical of sequence clusters detected in environmental clone libraries.

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The intent of this study was to evaluate the Guide on the Side (GotS), an online learning tool developed by the University of Arizona Libraries, and a screencast tutorial for teaching information literacy and database searching skills. Ninety undergraduate students were randomly assigned into three groups: group 1 completed a GotS tutorial; group 2 viewed a screencast presenting identical content; and a control group. Each group completed an identical 16-item post-test. An analysis of variance revealed statistically significant differences between the control group and both treatment groups; however, there was no statistical difference between treatment groups. Limitations of the study and future research areas are also discussed. 70[ARTICLE]

Purpose -The purpose of this paper is to describe the development and rationale for the creation of a scalable approach to online database instruction. Design/methodology/approach -The paper discusses the pedagogical, organizational, and technological considerations for developing an interactive, online tutorial that can be used by librarians for database instruction. Findings -Database instruction during one-shot library sessions is a cornerstone of information literacy programs, but with a move to online instruction, it has not been clear how to replicate many of the pedagogical advantages that take place in a face-to-face environment. Librarians along with programmers have developed a new type of scalable and pedagogically-sound interactive tutorial. Originality/value -The paper provides librarians with a history of the development of a tutorial that has been released as open-source software program that can be easily modified by other libraries.

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