Role of Two Cell Wall Amidases in Septal Junction and Nanopore Formation in the Multicellular Cyanobacterium Anabaena sp. PCC 7120

Frontiers in Cellular and Infection Microbiology

Perez, Rebeca¹  Flores, Enrique²  Silber, Nadine²  Bornikoel, Jan³  Fan, Qing⁶  Carrió⁷  n, Alejandro⁸  Mullineaux, Conrad W.⁹  Forchhammer, Karl^1,10  Wolk, C. Peter^1,10  Maldener, Iris^1,11  Mariscal, Vicente^1,11 

[1] Department of Microbiology-Immunology, Feinberg School of Medicine of Northwestern University, Chicago, IL, United States;Instituto de BioquíInterfaculty Institute of Microbiology and Infection Medicine TüMSU-DOE Plant Research Laboratory and Department of Plant Biology, Michigan State University, East Lansing, MI, United States;School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom;bingen, Germany;bingen, Organismic Interactions, University of Tübingen, Tüficas and Universidad de Sevilla, Seville, Spain;mica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Cientí

关键词: Cyanobacteria;    Heterocysts;    Peptidoglycan;    Amidase;    AMIC;    septal junctions;    cell-cell communication;    SepJ;   

DOI  :  10.3389/fcimb.2017.00386

学科分类：生物科学（综合）

来源: Frontiers

【 摘 要 】

Filamentous cyanobacteria have developed a strategy to perform incompatible processes in one filament by differentiating specialized cell types, N2-fixing heterocysts and CO2-fixing, photosynthetic, vegetative cells. These bacteria can be considered true multi-cellular organisms with cells exchanging metabolites and signaling molecules via septal junctions, involving the SepJ and FraCD proteins. Previously, it was shown that the cell wall lytic N-acetylmuramyl-L-alanine amidase, AmiC2, is essential for cell-cell communication in Nostoc punctiforme. This enzyme perforates the septal peptidoglycan creating an array of nanopores, which may be the framework for septal junction complexes. In Anabaena sp. PCC 7120, two homologs of AmiC2, encoded by amiC1 and amiC2, were identified and investigated in two different studies. Here, we compare the function of both AmiC proteins by characterizing different Anabaena amiC mutants, which was not possible in N. punctiforme, because there the amiC1 gene could not be inactivated. This study shows the different impact of each protein on nanopore array formation, the process of cell-cell communication, septal protein localization and heterocyst differentiation. Inactivation of either amidase resulted in significant reduction in nanopore count and in the rate of fluorescent tracer exchange between neighboring cells measured by FRAP analysis. In an amiC1 amiC2 double mutant, filament morphology was affected and heterocyst differentiation was abolished. Furthermore, the inactivation of amiC1 influenced SepJ localization and prevented the filament-fragmentation phenotype that is characteristic of sepJ or fraC fraD mutants. Our findings suggest that both amidases are to some extent redundant in their function, and describe a functional relationship of AmiC1 and septal proteins SepJ and FraCD.

【 授权许可】

CC BY