THE BACTERIAL NUCLEOID VISUALIZED BY FLUORESCENCE MICROSCOPY OF CELLSLYSED WITHIN AGAROSE - COMPARISON OF ESCHERICHIA-COLI AND SPIROCHETESOF THE GENUS BORRELIA

The nucleoids of Escherichia coli and the spirochetes Borrelia burgdor feri and Borrelia hermsii, agents of Lyme disease and relapsing fever, were examined by epifluorescence microscopy of bacterial cells embedd ed in agarose and lysed in situ with detergent and protease, The typic al E. coli nucleoid was a rosette in which 20 to 50 long loops of DNA emanated from a dense node of DNA, The percentages of cells in a popul ation having nucleoids,vith zero, one, two, and three nodes varied wit h growth rate and growth phase, The borrelia nucleoid, in contrast, wa s a loose network of DNA strands devoid of nodes, This nucleoid struct ure difference correlates with the unusual genome of Borrelia species, which consists primarily of linear replicons, including a 950-kb line ar chromosome and linear plasmids, This method provides a simple, dire ct means to analyze the structure of the bacterial nucleoid.