Background
Listeria monocytogenes
is a gram-positive bacterium that causes listeriosis mainly in immunocompromised hosts. It can also cause foodborne outbreaks and has the ability to adapt to various environments. Peptide uptake in gram-positive bacteria is enabled by oligopeptide permeases (Opp) in a process that depends on ATP hydrolysis by OppD and F. Previously a putative protein Lmo2193 was predicted to be OppD, but little is known about the role of OppD in major processes of
L. monocytogenes
, such as growth, virulence, and biofilm formation.
Objectives
To determine whether the virulence traits of
L. monocytogenes
are related to OppD.
Methods
In this study,
lmo2193
gene deletion and complementation strains of
L. monocytogenes
were generated and compared with a wild-type strain for the following: adhesiveness, invasion ability, intracellular survival, proliferation, 50% lethal dose (LD
50
) to mice, and the amount bacteria in the mouse liver, spleen, and brain.
Results
The results showed that virulence of the deletion strain was 1.34 and 0.5 orders of magnitude higher than that of the wild-type and complementation strains, respectively. The function of Lmo2193 was predicted and verified as OppD from the ATPase superfamily. Deletion of
lmo2193
affected the normal growth of
L. monocytogenes
, reduced its virulence in cells and mice, and affected its ability to form biofilms.
Conclusions
Deletion of the oligopeptide transporter Lmo2193 decreases the virulence of
L. monocytogenes
. These effects may be related to OppD's function, which provides a new perspective on the regulation of oligopeptide transporters in
L. monocytogenes
.
The aim of the present study was to explore the effects of different dietary levels (0, 15, 30, 60, 120 mg/kg) of leonurine hydrochloride (LHy) supplementation on growth performance, immune response, antioxidant capacity, hematological parameters and serum lipid profiles in broiler chicks. A total of 600 1-day-old Ross × Ross male broilers were randomly allocated to five treatment groups consisting of eight pens of fifteen birds. The feeding programme included a starter diet until day 21 and a finisher diet from day 22 to day 42. The results indicate that LHy did not alter the growth performance of broilers (P > 0.05). Supplementation of the basal diet with LHy increased (linear, P < 0.05) relative spleen weights at d 21 and 42. In both 21-and 42-day-old chicks, dietary LHy supplementation linearly increased (P < 0.05) the serum immunoglobulin A (IgA) and M (IgM) concentrations, catalase (CAT), total superoxide dismutase (T-SOD), total antioxidant capacity (T-AOC) activities, low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) levels, while linearly (P < 0.05) decreased serum malondialdehyde (MDA) activity, red blood cell (RBC) count, hemoglobin, triglyceride (TC) levels and total cholesterol (CHOL) content. In addition dietary LHy supplementation linearly (P < 0.05) increased the GSH activity in 42-day-old broilers. Taken together, dietary LHy supplementation was able to promote immune function and antioxidant capacity, and decrease blood lipid levels in broilers.
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