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Vol. 155, No. 1JOURNAL OF BACTERIOLOGY, July 1983, p. 367-380 0021-9193/83/070367-14$02.00/0
 

Summary: Vol. 155, No. 1JOURNAL OF BACTERIOLOGY, July 1983, p. 367-380
0021-9193/83/070367-14$02.00/0
Copyright 1983, American Society for Microbiology
Ultrastructural Analysis of Ineffective Alfalfa Nodules Formed
by nif::TnS Mutants of Rhizobium meliloti
ANN M. HIRSCH,1 MISUK BANG,2t AND FREDERICK M. AUSUBEL2t*
Department ofBiological Sciences, Wellesley College, Wellesley, Massachusetts 02181,1 and Department of
Cellular and Developmental Biology, Harvard University, Cambridge, Massachusetts 021382
Received 15 February 1983/Accepted 29 April 1983
Ineffective alfalfa nodules formed by Rhizobium meliloti nif: :Tn5 mutants were
examined by light and electron microscopy. R. meliloti nifp::Tn5 mutants formed
nodules that were similar in structure to wild-type nodules except that nifH-
bacteroids accumulated a compact, electron-dense body. In contrast to nodules
induced by wild type and nifH mutants, nifDK- R. meliloti mutants induced
nodules which contained numerous starch grains and prematurely senescent
bacteroids. In addition, meristematic activity in nifDK- nodules ceased signifi-
cantly earlier than in nifH- nodules. All mutant nodules exhibited elevated levels
of rough endoplasmic reticulum and Golgi membranes compared to wild-type
nodule cells. These elevated levels may reflect either a response to nitrogen
starvation in the ineffective nodules or an abnormal synthesis and export of

  

Source: Ausubel, Frederick M. - Department of Genetics, Harvard University

 

Collections: Biology and Medicine