FTIR spectra of <i>L. monocytogenes</i> re-isolated from challenged mice.

<p>(A) Average FTIR spectra derived from 129/Sv (dotted), Tyk2−/− (dashed) and C57BL/6 (solid) isolates are shown from the whole spectral range (B) Subtraction spectra were generated from second derivative, vector-normalized, average FTIR spectra of the three different mouse genotypes. Spectra from C57BL/6 mice were subtracted from 129/Sv isolates (black), spectra from C57BL/6 mice were subtracted from Tyk2−/− (red) and spectra from Tyk2−/− were subtracted from 129/Sv isolates (blue). Most pronounced differences were observed in the spectral range of 1700–1500 cm⁻¹ (protein region) and can be assigned to amide I (1670–1625 cm⁻¹) and amide II (1560–1530 cm⁻¹).</p

Survival rates of different mouse genotypes challenged with <i>L. monocytogenes</i>.

<p>Mice of the indicated genotypes (n = 8 mice/group) were infected with 5×10⁴ cfu bacteria intraperitoneally and survival was monitored over a 12-day period.</p

ANOVA-pairwise comparison to assess significant differentiation among the three genotypes (<i>p</i>-values).

<p>ANOVA-pairwise comparison to assess significant differentiation among the three genotypes (<i>p</i>-values).</p

Deciphering Host Genotype-Specific Impacts on the Metabolic Fingerprint of <i>Listeria monocytogenes</i> by FTIR Spectroscopy

<div><p>Bacterial pathogens are known for their wide range of strategies to specifically adapt to host environments and infection sites. An in-depth understanding of these adaptation mechanisms is crucial for the development of effective therapeutics and new prevention measures. In this study, we assessed the suitability of Fourier Transform Infrared (FTIR) spectroscopy for monitoring metabolic adaptations of the bacterial pathogen <i>Listeria monocytogenes</i> to specific host genotypes and for exploring the potential of FTIR spectroscopy to gain novel insights into the host-pathogen interaction. Three different mouse genotypes, showing different susceptibility to <i>L. monocytogenes</i> infections, were challenged with <i>L. monocytogenes</i> and re-isolated bacteria were subjected to FTIR spectroscopy. The bacteria from mice with different survival characteristics showed distinct IR spectral patterns, reflecting specific changes in the backbone conformation and the hydrogen-bonding pattern of the protein secondary structure in the bacterial cell. Coupling FTIR spectroscopy with chemometrics allowed us to link bacterial metabolic fingerprints with host infection susceptibility and to decipher longtime memory effects of the host on the bacteria. After prolonged cultivation of host-passaged bacteria under standard laboratory conditions, the host's imprint on bacterial metabolism vanished, which suggests a revertible metabolic adaptation of bacteria to host environment and loss of host environment triggered memory effects over time. In summary, our work demonstrates the potential and power of FTIR spectroscopy to be used as a fast, simple and highly discriminatory tool to investigate the mechanism of bacterial host adaptation on a macromolar and metabolic level.</p></div

Host imprint on mice passaged <i>L. monocytogenes</i> isolates monitored be FTIR spectroscopy.

<p>LDA was carried out on second derivative, vector-normalized FTIR spectra from <i>L. monocytogenes</i> re-isolated from challenged 129/Sv (X), Tyk2−/− (O) and C57BL/6 (+) mice derived from the two independent experiments.</p

Potential host memory effects on mice passaged <i>L. monocytogenes</i> isolates monitored by FTIR spectroscopy.

<p>PCA on second derivative, vector-normalized FTIR spectra from <i>L. monocytogenes</i> isolates derived from challenged 129/Sv (X), Tyk2−/− (O) and C57BL/6 (+) mice from one representative experiment (A) directly after passage in mice and after consecutive sub-cultivations at 37°C on laboratory standard media for one week (B) and for 6 weeks (C).</p