Microbiology Session
Patrick Preissler, Technische Universität München, Freising, Germany
Co-author(s): Jürgen Behr and Rudi Vogel, Technische Universität München, Freising, Germany
ABSTRACT: Manganese is an essential metal for lactic acid
bacteria, which is part of many enzymes, often replacing (redox)
functions of iron in enzymes of other bacteria. As bacteria lack
compartmentation, metal ion homeostasis is maintained primarily by
regulation of metal cation flux across the cell membrane. It has been
shown that hop compounds induce efflux of manganese, which is part of
bacterial stress response and adaptation to iso-alpha-acids. On the
other hand, the permeability of the membrane is adjusted through its
membrane lipid composition, which may influence (manganese) transporter
effectiveness and also intrusion of weak acids and other antibiotic
compounds. As a result, a decrease in membrane fluidity could contribute
to hop tolerance and beer-spoiling ability. In this study, we have
investigated the influence of initial intracellular manganese levels and
incubation in lager beer on the effects of metal trace elements and the
composition of fatty acids in the cell membrane. Cells of beer-spoiling
Lactobacillus brevis TMW 1.313 exhibited reduction of manganese
and decreasing zinc concentrations after adaptation to the beer
environment. At the same time, intracellular calcium, iron, and
magnesium levels were increased. The analysis of cytoplasmic fatty acids
composition showed that adaptation to beer after 5 days of incubation
resulted in a reduction of the amounts of saturated fatty acids 12:0 and
16:0 3OH, whereas those of the two cyclic fatty acids (17:0 and 19:0),
as well as the saturated fatty acid 18:0 and the unsaturated 20:2 ,were
increased in the cell membrane. In conclusion, both tuning of the
membrane composition and balanced metal ion content contributed to
improved survival of L. brevis in beer by reduction of hop
sensitivity and concomitant acid stress. This may indicate that
functionality of metal ion transporters is modulated in such a membrane
and both traits are connected.
Patrick Preissler was born in
1981 in Erfurt, the regional capital of Thuringia. He studied nutrition
science at Friedrich-Schiller-Universität in Jena. In 2011 he finished
his Ph.D. thesis on mechanisms of hop tolerance in beer-spoiling Lactobacillus brevis
at Technische Universität München under the supervision of Rudi F.
Vogel at the Chair of Technische Mikrobiologie in Weihenstephan.
