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Title:Molecular analysis of the extrachromosomal elements of Lactobacillus acidophilus strain 100-33
Author(s):Rinckel, Lori Ann
Doctoral Committee Chair(s):Salyers, Abigail A.
Department / Program:Microbiology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Molecular
Biology, Microbiology
Abstract:My thesis details studies of the extrachromosomal elements of Lactobacillus acidophilus strain 100-33. Strain 100-33 has antibiotic resistance to macrolide, lincosamide, and streptogramin B-type antibiotics (MLS$\sp{\rm R}$) and tetracycline. Transformants with altered plasmid profiles had also become sensitive to the MLS antibiotics (McCarthy et al, 1988).
This MLS$\sp{\rm R}$ was localized to an 18 kbp plasmid, pLAR33, in strain 100-33. This plasmid was found to be present not only in monomeric form, but as multimers as well. An MLS$\sp{\rm R}$ derivative of strain 100-33, strain ES1, was produced. Strain ES1 possesses an 11 kbp plasmid, pLARES1. This plasmid is also present in multimeric forms. Restriction analysis indicates that pLARES1 is a deleted form of pLAR33 which has lost a 7 kbp region containing the MLS$\sp{\rm R}$ determinant.
Data indicate that the MLS$\sp{\rm R}$ determinant from pLAR33 is contained on a transposable element and that this element has been deleted to form pLARES1 from pLAR33. This transposable element, Tn5371, is the first transposon discovered in the lactobacilli which carries a selectable marker.
Further investigations into pLAR33 and pLARES1 indicate that these plasmids replicate by forming single stranded plasmid DNA intermediates. This finding suggests that these plasmids replicate by a rolling circle type of replication (Gruss and Ehrlich, 1989). Such an observation is unique; plasmids from other genera of Gram positive bacteria reported to replicate by a rolling circle type of mechanism have all been less than 7 kbp in size. These plasmids are stably maintained by their bacterial hosts, not only in a monomeric form, but in several multimeric forms as well. The replication origin of pLAR33 was localized to a 2.3 kbp PstI-EcoRI restriction fragment. This region was further analyzed by Tn1000 mutagenesis. Further research is necessary to elucidate the mechanisms by which these plasmids are stably maintained and replicate by this mechanism. (Abstract shortened with permission of author.)
Issue Date:1992
Rights Information:Copyright 1992 Rinckel, Lori Ann
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9215878
OCLC Identifier:(UMI)AAI9215878

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