Abstract
ABSTRACT
Listeria monocytogenes
integrates into multi-species biofilms and persists in food processing facilities. Its persistence depends on the composition of the microbial communities, but those species that accommodate
L. monocytogenes
, or not, remain to be identified. Moreover, the decision-making on biofilm vs pellicle formation in microbial communities remains poorly understood. It was the aim of this study to identify communities that accommodate
Listeria
, or not, and to observe biofilm vs pellicle formation in multi-species biofilms. We quantified
L. monocytogenes
in six reconstituted communities, each consisting of 5–19 strains. A 15-member community was simplified into five species to quantify
L. monocytogenes
in all 31 combinations of these five strains.
Janthinobacterium tructae
favored pellicle formation, while
Pseudomonas shahriarae
convinced others to join a surface-attached biofilm. In the six microbial communities, cell counts of
L. monocytogenes
were lowest when
Carnobacterium maltaromaticum
was also present. The antagonistic effect of
C. maltaromaticum
was confirmed when analyzing all combinations of five strains. The presence of
C. maltaromaticum
reduced cell counts of
L. monocytogenes
by about 1 log CFU/cm
2
.
Serratia liquefaciens
also antagonized
L. monocytogenes
, but this was observed (
P
C. maltaromaticum
. Genome analyses of the community identified close to 100 different quorum-sensing systems, including peptides that are also bactericidal against
L. monocytogenes
. We conclude that the language used to describe human social interactions is also suited to describe microbial interactions in multi-species biofilm communities, but unraveling mechanisms of communication among biofilm-embedded bacteria remains subject to future studies.
IMPORTANCE
Microbial communication in relation to biofilm vs pellicle formation and on whether to accommodate
Listeria monocytogene
s or not partially converge with quorum-sensing systems as a key mechanism. Two organisms,
Carnobacterium maltaromaticum
and
Serratia liquefaciens
, antagonized
L. monocytogenes
. Microbial interactions are strongly dependent on the complexity of the microbial community, and different behaviors were observed in biofilms formed by 2, 5, or 15 strains. Results presented in this study document that the use of protective cultures may also reduce persistence of
Listeria
in food processing facilities but are far from providing an understanding of communication and social rules in complex bacterial communities. The novel perspective on microbial interactions may direct future experiments.