Khan, R. N. | bioRxiv Science

bioRxiv2021

Lactococcus lactis sb. cremoris orchestrates signal events in the gut epithelium via TLR2 to promote tissue restitution

The use of beneficial bacteria to promote gastrointestinal heath is widely practiced, however, the mechanisms whereby many of these microbes elicit their beneficial effects remain elusive. Previously, we conducted a screen for the discovery of novel beneficial microbes and identified the potent cytoprotective effects of a strain of Lactococcus lactis subsp. cremoris. Here, we show that dietary supplementation with L. lactis subsp. cremoris induced transcript enrichment of a set of genes within the colon whose functions are associated with host cell and microbe interactions. Specifically, L. lactis subsp. cremoris induced the expression of tlr2, which we show was required for L. lactis subsp. cremoris to elicit its beneficial effects on the intestine. L. lactis subsp. cremoris did not confer beneficial effects in mice deficient in TLR-2, or deficient in its adaptor protein Myd88 in chronic gut injury models. In addition to cytoprotection, culture supernatant from L. lactis subsp. cremoris accelerated epithelial migration in a cultured epithelial cell scratch wound assay; and effect that was abrogated by a TLR-2 antagonist. Furthermore, L. lactis subsp. cremoris accelerated epithelial tissue restitution following the infliction of a colonic wound biopsy in a TLR-2 and Myd88-dependent manner. Within colonic wounds, L. lactis subsp. cremoris induced the activation of signaling pathways that function in tissue restitution following injury, including the ERK signaling pathway, and of focal adhesion complex (FAC) proteins. Together, these data demonstrate that L. lactis subsp. cremoris signals via the TLR2/MyD88-axis to confer cytoprotection and accelarated tissue restituion in the gut epithelium. These data point to evolving adaptations where beneficial gut microbes moduate innate immune signaling to excert positive influnces on host physiology.

microbiology↗

bioRxiv2021

Song preferences predict the quality of vocal learning in zebra finches

In songbirds, learning to sing is a highly social process that likely involves social reward. Here, we hypothesized that the degree to which a juvenile songbird learns a song depends on the degree to which it finds that song rewarding to hear during vocal development. We tested this hypothesis by measuring song preferences in young birds during song learning and then analyzing their adult songs. Song preferences were measured in an operant key-pressing assay. Juvenile male zebra finches (Taeniopygia guttata) had access to two keys, each of which was associated with a higher likelihood of playing the song of their father or that of another familiar adult ("neighbor"). To minimize the effects of exposure on learning, we implemented a reinforcement schedule that allowed us to detect preferences while balancing exposure to each song. On average, the juveniles significantly preferred the fathers song early during song learning, before they were themselves singing. At around post-hatch day 60, their preference shifted to the neighbors song. At the end of the song learning period, we recorded the juveniles songs and compared them to the fathers and the neighbors song. All of the birds copied fathers song. The accuracy with which the fathers song was imitated was positively correlated with the peak strength of the preference for the fathers song during the sensitive period. Our results show that preference for a social stimulus, in this case a vocalization, predicted social learning during development.

animal behavior and cognition↗