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Elucidation of the B urkholderia cenocepacia hopanoid biosynthesis pathway uncovers functions for conserved proteins in hopanoid‐producing bacteria
Author(s) -
Schmerk Crystal L.,
Welander Paula V.,
Hamad Mohamad A.,
Bain Katie L.,
Bernards Mark A.,
Summons Roger E.,
Valvano Miguel A.
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12509
Subject(s) - hopanoids , biology , biochemistry , biosynthesis , bacteria , microbiology and biotechnology , mutant , enzyme , gene , paleontology , genetics , structural basin , source rock
Summary Hopanoids are bacterial surrogates of eukaryotic membrane sterols and among earth's most abundant natural products. Their molecular fossils remain in sediments spanning more than a billion years. However, hopanoid metabolism and function are not fully understood. B urkholderia species are environmental opportunistic pathogens that produce hopanoids and also occupy diverse ecological niches. We investigated hopanoids biosynthesis in B urkholderia cenocepacia by deletion mutagenesis and structural characterization of the hopanoids produced by the mutants. The enzymes encoded by hpnH and hpnG were essential for production of all C 35 extended hopanoids, including bacteriohopanetetrol ( BHT ), BHT glucosamine and BHT cyclitol ether. Deletion of hpnI resulted in BHT production, while Δ hpnJ produced only BHT glucosamine. Thus, HpnI is required for BHT glucosamine production while HpnJ is responsible for its conversion to the cyclitol ether. The Δ hpnH and Δ hpnG mutants could not grow under any stress condition tested, whereas Δ hpnI , Δ hpnJ and Δ hpnK displayed wild‐type growth rates when exposed to detergent, but varying levels of sensitivity to low pH and polymyxin B . This study not only elucidates the biosynthetic pathway of hopanoids in B . cenocepacia , but also uncovers a biosynthetic role for the conserved proteins HpnI , HpnJ and HpnK in other hopanoid‐producing bacteria.