Quantification of Movement Error from Spiral Drawing Test.

Parkinson's disease is a neurodegenerative disease that often comes with symptoms such as muscle stiffness, slowness of movement, and tremors at rest. Since this disease negatively influences the quality of life in patients, an early and accurate diagnosis is important for slowing the progression of the disease and providing effective treatment to patients. One of the quick and easy methods for diagnosing is the spiral drawing test and the differences between the target spiral picture and the drawing by patients can be used as an indicator of movement error. Simply, the average distance between paired samples of the target spiral and the drawing can be easily calculated and used as the level of movement error. However, finding the correct pair of samples between the target spiral and the drawing is relatively difficult, and the accurate algorithm to quantify the movement error has not been thoroughly studied. In this study, we propose algorithms applicable to the spiral drawing test, that ultimately can be used to measure the level of movement error in Parkinson's disease patients. They are equivalent inter-point distance (ED), shortest distance (SD), varying inter-point distance (VD), and equivalent angle (EA). To evaluate the performance and sensitivity of the methods, we collected data from simulation and experiments with healthy subjects and evaluated the four methods. As a result, in normal (good drawing) and severe symptom (poor drawing) conditions, the calculated errors were 3.67/5.48 from ED, 0.11/1.21 from SD, 0.38/1.46 from VD and 0.01/0.02 from EA, meaning that ED, SD, and VD measure movement error with high noise while EA is sensitive to even small symptom levels. Similarly, in the experiment data, only EA shows the linear increase of error distance to changing symptom levels from 1 to 3. In summary, we found that EA is the most effective algorithm in finding the correct pair of samples between the spiral and the drawing, and consequently yields low errors and high sensitivity to symptom levels.

Rotation-Time Symmetry Breaking in Frustrated Chiral Nematic Driven by a Pulse-Train Waveform.

We report waveform-induced rotation-time symmetry breaking in liquid crystal director motion. Homeotropic cells filled with a negative dielectric anisotropy chiral nematic exhibit persistent and visually observable waves of director orientation with a time period of at least 30 driving field cycles. Their existence in the space of driving waveform parameters is explored. The possibility of utilizing this system, which exhibits both spatial and temporal long-range order, as a modeling tool for experimental studies on discrete time crystals is discussed.

Retroreflection-based sandwich type affinity sensing of isothermal gene amplification products for foodborne pathogen detection.

Loop-mediated isothermal amplification (LAMP) is an outstanding method for molecular diagnostics, as the rapid, specific, and sensitive amplification of target genes is possible. However, it is necessary to measure fluorescence in the quantitative analysis of LAMP products, so a sophisticated optical setup is required. This study tried to develop a novel sensing method that can quantify target analytes with simple equipment, such as nonspectroscopic white light and a CMOS camera. To achieve this, a retroreflective Janus particle (RJP) as a probe and specially designed loop primers, fluorescein isothiocyanate (FITC)- and biotin-modified loop primers, were introduced into the LAMP system. By performing LAMP in the presence of designed primers, double-stranded amplicons possessing FITC and biotin labels at each end are generated in proportion to the quantity of the target pathogen. Using the anti-FITC antibody-modified sensing surface and streptavidin-conjugated RJP probes, the amplicons can be captured in sandwich-configuration and detected under nonspectroscopic conditions composed of white light and a camera. To confirm the feasibility of the sensing system, the invA gene of Salmonella was selected as the target. It was possible to quantitatively analyze the Salmonella concentration from 0 to 106 colony-forming units, sufficiently covering the required detection range. In addition, quantitative analyses of pathogens in contaminated food sources, including milk and chicken meat, were successfully conducted with a limit of detection of 10 CFU.

Roles of YcfR in Biofilm Formation in Salmonella Typhimurium ATCC 14028.

An increasing number of foodborne diseases are currently attributable to farm produce contaminated with enteric pathogens such as Salmonella enterica. Recent studies have shown that a variety of enteric pathogens are able to colonize plant surfaces by forming biofilms and thereby persist for long periods, which can subsequently lead to human infections. Therefore, biofilm formation by enteric pathogens on plants poses a risk to human health. Here, we deciphered the roles of YcfR in biofilm formation by Salmonella enterica. YcfR is a putative outer membrane protein associated with bacterial stress responses. The lack of YcfR facilitated the formation of multicellular aggregates on cabbage leaves as well as glass surfaces while reducing bacterial motility. ycfR deletion caused extensive structural alterations in the outer membrane, primarily in lipopolysaccharides, outer membrane proteins, cellulose, and curli fimbria, thereby increasing cell surface hydrophobicity. However, the absence of YcfR rendered Salmonella susceptible to stressful treatments, despite the increased multicellular aggregation. These results suggest that YcfR is an essential constituent of Salmonella outer membrane architecture and its absence may cause multifaceted structural changes, thereby compromising bacterial envelope integrity. In this context, YcfR may be further exploited as a potential target for controlling Salmonella persistence on plants.

Hfq plays important roles in virulence and stress adaptation in Cronobacter sakazakii ATCC 29544.

Cronobacter spp. are opportunistic pathogens that cause neonatal meningitis and sepsis with high mortality in neonates. Despite the peril associated with Cronobacter infection, the mechanisms of pathogenesis are still being unraveled. Hfq, which is known as an RNA chaperone, participates in the interaction with bacterial small RNAs (sRNAs) to regulate posttranscriptionally the expression of various genes. Recent studies have demonstrated that Hfq contributes to the pathogenesis of numerous species of bacteria, and its roles are varied between bacterial species. Here, we tried to elucidate the role of Hfq in C. sakazakii virulence. In the absence of hfq, C. sakazakii was highly attenuated in dissemination in vivo, showed defects in invasion (3-fold) into animal cells and survival (10(3)-fold) within host cells, and exhibited low resistance to hydrogen peroxide (10(2)-fold). Remarkably, the loss of hfq led to hypermotility on soft agar, which is contrary to what has been observed in other pathogenic bacteria. The hyperflagellated bacteria were likely to be attributable to the increased transcription of genes associated with flagellar biosynthesis in a strain lacking hfq. Together, these data strongly suggest that hfq plays important roles in the virulence of C. sakazakii by participating in the regulation of multiple genes.

Identification and characterization of outer membrane vesicle-associated proteins in Salmonella enterica serovar Typhimurium.

Salmonella enterica serovar Typhimurium is a primary cause of enteric diseases and has acquired a variety of virulence factors during its evolution into a pathogen. Secreted virulence factors interact with commensal flora and host cells and enable Salmonella to survive and thrive in hostile environments. Outer membrane vesicles (OMVs) released from many Gram-negative bacteria function as a mechanism for the secretion of complex mixtures, including virulence factors. We performed a proteomic analysis of OMVs that were isolated under standard laboratory and acidic minimal medium conditions and identified 14 OMV-associated proteins that were observed in the OMV fraction isolated only under the acidic minimal medium conditions, which reproduced the nutrient-deficient intracellular milieu. The inferred roles of these 14 proteins were diverse, including transporter, enzyme, and transcriptional regulator. The absence of these proteins influenced Salmonella survival inside murine macrophages. Eleven of these proteins were predicted to possess secretion signal sequences at their N termini, and three (HupA, GlnH, and PhoN) of the proteins were found to be translocated into the cytoplasm of host cells. The comparative proteomic profiling of OMVs performed in this study revealed different protein compositions in the OMVs isolated under the two different conditions, which indicates that the OMV cargo depends on the growth conditions and provides a deeper insight into how Salmonella utilizes OMVs to adapt to environmental changes.

Genomic investigation of lysogen formation and host lysis systems of the Salmonella temperate bacteriophage SPN9CC.

To understand phage infection and host cell lysis mechanisms in pathogenic Salmonella, a novel Salmonella enterica serovar Typhimurium-targeting bacteriophage, SPN9CC, belonging to the Podoviridae family was isolated and characterized. The phage infects S. Typhimurium via the O antigen of lipopolysaccharide (LPS) and forms clear plaques with cloudy centers due to lysogen formation. Phylogenetic analysis of phage major capsid proteins revealed that this phage is a member of the lysogen-forming P22-like phage group. However, comparative genomic analysis of SPN9CC with P22-like phages indicated that their lysogeny control regions and host cell lysis gene clusters show very low levels of identity, suggesting that lysogen formation and host cell lysis mechanisms may be diverse among phages in this group. Analysis of the expression of SPN9CC host cell lysis genes encoding holin, endolysin, and Rz/Rz1-like proteins individually or in combinations in S. Typhimurium and Escherichia coli hosts revealed that collaboration of these lysis proteins is important for the lysis of both hosts and that holin is a key protein. To further investigate the role of the lysogeny control region in phage SPN9CC, a ΔcI mutant (SPN9CCM) of phage SPN9CC was constructed. The mutant does not produce a cloudy center in the plaques, suggesting that this mutant phage is virulent and no longer temperate. Subsequent comparative one-step growth analysis and challenge assays revealed that SPN9CCM has shorter eclipse/latency periods and a larger burst size, as well as higher host cell lysis activity, than SPN9CC. The present work indicates the possibility of engineering temperate phages as promising biocontrol agents similar to virulent phages.

Rapid Dot-Blot Immunoassay for Detecting Multiple Salmonella enterica Serotypes.

Salmonella, a major contributor to foodborne infections, typically causes self-limiting gastroenteritis. However, it is frequently invasive and disseminates across the intestinal epithelium, leading to deadly bacteremia. Although the genus is subdivided into >2,600 serotypes based on their antigenic determinants, only few serotypes are responsible for most human infections. In this study, a rapid dot-blot immunoassay was developed to diagnose multiple Salmonella enterica serotypes with high incidence rates in humans. The feasibility of 10 commercial antibodies (four polyclonal and six monoclonal antibodies) was tested using the 18 serotypes associated with 67.5% Salmonella infection cases in the United States of America (U.S.A) in 2016. Ab 3 (polyclonal; eight of 18 serotypes), Ab 8 (monoclonal; 13 of 18 serotypes), and Ab 9 (monoclonal; 10 of 18 serotypes) antibodies exhibited high detection rates in western blotting and combinations of two antibodies (Ab 3+8, Ab 3+9, and Ab 8+9) were applied to dot-blot assays. The combination of Ab 3+8 identified 15 of the tested 18 serotypes in 3 h, i.e., S. Enteritidis, S. Typhimurium, S. Javiana, S. I 4,[5],12:i:-, S. Infantis, S. Montevideo, S. Braenderup, S. Thompson, S. Saintpaul, S. Heidelberg, S. Oranienburg, S. Bareilly, S. Berta, S. Agona, and S. Anatum, which were responsible for 53.7% Salmonella infections in the U.S. in 2016. This cost-effective and rapid method can be utilized as an on-site colorimetric method for Salmonella detection.

Unveiling the mechanism of bactericidal activity of a cecropin A-fused endolysin LNT113.

Endolysins are lytic enzymes produced by bacteriophages at the end of their lytic cycle and degrade the peptidoglycan layer of the bacterial cell wall. Thus, they have been extensively explored as a promising antibacterial agent to replace or supplement current antibiotics. Gram-negative bacteria, however, are prone to resist exogenous endolysins owing to their protective outer membrane. We previously engineered endolysin EC340, encoded by the Escherichia coli phage PBEC131, by substituting its seven amino acids and fusing an antimicrobial peptide cecropin A at its N-terminus. The engineered endolysin LNT113 exerted superior activity to its intrinsic form. This study investigated how cecropin A fusion facilitated the bactericidal activity of LNT113 toward Gram-negative bacteria. Cecropin A of LNT113 markedly increased the interaction with lipopolysaccharides, while the E. coli defective in the core oligosaccharide was less susceptible to endolysins, implicating the interaction between the core oligosaccharide and endolysins. In fact, E. coli with compromised lipid A construction was more vulnerable to LNT113 treatment, suggesting that the integrity of the lipid A layer was important to resist the internalization of LNT113 across the outer membrane. Cecropin A fusion further accelerated the inner membrane destabilization, thereby enabling LNT113 to deconstruct it promptly. Owing to the increased membrane permeability, LNT113 could inactivate some Gram-positive bacteria as well. This study demonstrates that cecropin A fusion is a feasible method to improve the membrane permeability of endolysins in both Gram-negative and Gram-positive bacteria.

Exploring the therapeutic potential of endolysin CD27L_EAD against Clostridioides difficile infection.

OBJECTIVES: Clostridioides difficile has emerged as a major cause of life-threatening diarrheal disease. Conventional antibiotics used in current standards of care exacerbate the emergence of antibiotic-resistant strains and pose a risk of recurrent C. difficile infection (CDI). Thus, there is an urgent need for alternative therapeutics that selectively eliminate C. difficile without disturbing the commensal microbiota. This study aimed to explore the potential of endolysins as an alternative therapeutic agent to antibiotics. Endolysin is a bacteriophage-derived peptidoglycan hydrolase that aids in the release of phage progeny during the final stage of infection. METHODS: In order to exploit endolysin as a therapeutic agent against CDI, the bactericidal activity of 23 putative endolysins was compared and ΦCD27 endolysin CD27L was selected and modified to CD27L_EAD by cleaving the cell-wall binding domain of CD27L. RESULTS: CD27L_EAD exhibited greater bacteriolytic activity than CD27L and its activity was stable over a wide range of salt concentrations and pH conditions. CD27L_EAD was added to a co-culture of human gut microbiota with C. difficile and the bacterial community structure was analyzed. CD27L_EAD did not impair the richness and diversity of the bacterial population but remarkably attenuated the abundance of C. difficile. Furthermore, the co-administration of vancomycin exerted synergistic bactericidal activity against C. difficile. ß-diversity analysis revealed that CD27L_EAD did not significantly disturb the composition of the microbial community, whereas the abundance of some species belonging to the family Lachnospiraceae decreased after CD27L_EAD treatment. CONCLUSIONS: This study provides insights into endolysin as a prospective therapeutic agent for the treatment of CDI without damaging the normal gut microbiota.

Blanket antimicrobial resistance gene database with structural information, BOARDS, provides insights on historical landscape of resistance prevalence and effects of mutations in enzyme structure.

Antimicrobial resistance (AMR) in pathogenic bacteria poses a significant threat to public health, yet there is still a need for development in the tools to deeply understand AMR genes based on genetic or structural information. In this study, we present an interactive web database named Blanket Overarching Antimicrobial-Resistance gene Database with Structural information (BOARDS, sbml.unist.ac.kr), a database that comprehensively includes 3,943 reported AMR gene information for 1,997 extended spectrum beta-lactamase (ESBL) and 1,946 other genes as well as a total of 27,395 predicted protein structures. These structures, which include both wild-type AMR genes and their mutants, were derived from 80,094 publicly available whole-genome sequences. In addition, we developed the rapid analysis and detection tool of antimicrobial-resistance (RADAR), a one-stop analysis pipeline to detect AMR genes across whole-genome sequencing (WGSs). By integrating BOARDS and RADAR, the AMR prevalence landscape for eight multi-drug resistant pathogens was reconstructed, leading to unexpected findings such as the pre-existence of the MCR genes before their official reports. Enzymatic structure prediction-based analysis revealed that the occurrence of mutations found in some ESBL genes was found to be closely related to the binding affinities with their antibiotic substrates. Overall, BOARDS can play a significant role in performing in-depth analysis on AMR.IMPORTANCEWhile the increasing antibiotic resistance (AMR) in pathogen has been a burden on public health, effective tools for deep understanding of AMR based on genetic or structural information remain limited. In this study, a blanket overarching antimicrobial-resistance gene database with structure information (BOARDS)-a web-based database that comprehensively collected AMR gene data with predictive protein structural information was constructed. Additionally, we report the development of a RADAR pipeline that can analyze whole-genome sequences as well. BOARDS, which includes sequence and structural information, has shown the historical landscape and prevalence of the AMR genes and can provide insight into single-nucleotide polymorphism effects on antibiotic degrading enzymes within protein structures.

Characterization and genomic analysis of two Staphylococcus aureus bacteriophages isolated from poultry/livestock farms.

Staphylococcus aureus is one of the most important pathogens, causing various diseases in humans and animals. As methicillin-resistant S. aureus (MRSA) has become increasingly prevalent, controlling this pathogen with standard antibiotic treatment has become challenging. Bacteriophages (phages) have attracted interest as alternative antibacterial agents to control MRSA. In this study, we isolated six S. aureus phages from soils of poultry/livestock farms. Based on the results of host range determination with 150 S. aureus strains and restriction enzyme treatment of phage DNA, two phages, designated SP5 and SP6, were selected for further characterization and genome sequencing. Both SP5 and SP6 were classified as members of the family Siphoviridae. The genome of SP5 comprises 43 305 bp and contains 63 ORFs, while the SP6 genome comprises 42 902 bp and contains 61 ORFs. Although they have different host spectra, the phage genomes exhibit high nucleotide similarity to each other. Adsorption assay results suggested that the host range determinants of the two phages are involved in both adsorption and infection. Comparative genomic analyses of the two phages provided evidence that the lysogenic/lytic control module and tail proteins may be important for host specificity.

Salmonella pathogenicity island 2 expression negatively controlled by EIIANtr-SsrB interaction is required for Salmonella virulence.

SsrA/SsrB is a primary two-component system that mediates the survival and replication of Salmonella within host cells. When activated, the SsrB response regulator directly promotes the transcription of multiple genes within Salmonella pathogenicity island 2 (SPI-2). As expression of the SsrB protein is promoted by several transcription factors, including SsrB itself, the expression of SPI-2 genes can increase to undesirable levels under activating conditions. Here, we report that Salmonella can avoid the hyperactivation of SPI-2 genes by using ptsN-encoded EIIA(Ntr), a component of the nitrogen-metabolic phosphotransferase system. Under SPI-2-inducing conditions, the levels of SsrB-regulated gene transcription increased abnormally in a ptsN deletion mutant, whereas they decreased in a strain overexpressing EIIA(Ntr). We found that EIIA(Ntr) controls SPI-2 genes by acting on the SsrB protein at the posttranscriptional level. EIIA(Ntr) interacted directly with SsrB, which prevented the SsrB protein from binding to its target promoter. Finally, the Salmonella strain, either lacking the ptsN gene or overexpressing EIIA(Ntr), was unable to replicate within macrophages, and the ptsN deletion mutant was attenuated for virulence in mice. These results indicated that normal SPI-2 gene expression maintained by an EIIA(Ntr)-SsrB interaction is another determinant of Salmonella virulence.

Cyclic di-GMP Modulates a Metabolic Flux for Carbon Utilization in Salmonella enterica Serovar Typhimurium.

Salmonella enterica serovar Typhimurium is an enteric pathogen spreading via the fecal-oral route. Transmission across humans, animals, and environmental reservoirs has forced this pathogen to rapidly respond to changing environments and adapt to new environmental conditions. Cyclic di-GMP (c-di-GMP) is a second messenger that controls the transition between planktonic and sessile lifestyles, in response to environmental cues. Our study reveals the potential of c-di-GMP to alter the carbon metabolic pathways in S. Typhimurium. Cyclic di-GMP overproduction decreased the transcription of genes that encode components of three phosphoenolpyruvate (PEP):carbohydrate phosphotransferase systems (PTSs) allocated for the uptake of glucose (PTSGlc), mannose (PTSMan), and fructose (PTSFru). PTS gene downregulation by c-di-GMP was alleviated in the absence of the three regulators, SgrS, Mlc, and Cra, suggesting their intermediary roles between c-di-GMP and PTS regulation. Moreover, Cra was found to bind to the promoters of ptsG, manX, and fruB. In contrast, c-di-GMP increased the transcription of genes important for gluconeogenesis. However, this effect of c-di-GMP in gluconeogenesis disappeared in the absence of Cra, indicating that Cra is a pivotal regulator that coordinates the carbon flux between PTS-mediated sugar uptake and gluconeogenesis, in response to cellular c-di-GMP concentrations. Since gluconeogenesis supplies precursor sugars required for extracellular polysaccharide production, Salmonella may exploit c-di-GMP as a dual-purpose signal that rewires carbon flux from glycolysis to gluconeogenesis and promotes biofilm formation using the end products of gluconeogenesis. This study sheds light on a new role for c-di-GMP in modulating carbon flux, to coordinate bacterial behavior in response to hostile environments. IMPORTANCE Cyclic di-GMP is a central signaling molecule that determines the transition between motile and nonmotile lifestyles in many bacteria. It stimulates biofilm formation at high concentrations but leads to biofilm dispersal and planktonic status at low concentrations. This study provides new insights into the role of c-di-GMP in programming carbon metabolic pathways. An increase in c-di-GMP downregulated the expression of PTS genes important for sugar uptake, while simultaneously upregulating the transcription of genes important for bacterial gluconeogenesis. The directly opposing effects of c-di-GMP on sugar metabolism were mediated by Cra (catabolite repressor/activator), a dual transcriptional regulator that modulates the direction of carbon flow. Salmonella may potentially harness c-di-GMP to promote its survival and fitness in hostile environments via the coordination of carbon metabolic pathways and the induction of biofilm formation.

Transcriptional insight into the effect of benzalkonium chloride on resistance and virulence potential in Salmonella Typhimurium.

Benzalkonium chloride (BC), a class of quaternary ammonium compounds (QACs), is widely used as a surface disinfectant in food industries and hospitals. To date, little is known about the underlying mechanisms of how bacterial pathogens respond to and develop resistance against QACs. We investigated the genome-wide transcriptional responses of Salmonella enterica serovar Typhimurium to treatment with BC and identified the genetic determinants required for bacterial resistance to BC, including ramRA, phoU-pstBACS, cpxARP, and ugpQCEAB. Remarkably, RamA, a member of the AraC/XylS family transcription regulators, increased its transcription upon treatment with BC and its absence rendered Salmonella susceptible to BC treatment, indicating the positive role of RamA in BC tolerance. The attenuated BC resistance of the ΔramA mutant strain was complemented by the introduction of AcrA in trans, indicating that the AcrAB-TolC efflux system activated by RamA is required for the resistance of Salmonella to BC. Meanwhile, sublethal concentrations of BC downregulated the mRNA expression of genes associated with Salmonella pathogenicity island 1 (SPI-1) and SPI-2, which are critical determinants of Salmonella virulence. In accordance with the downregulation of SPI-1, HilD, the master regulator of SPI-1, also decreased upon treatment with BC; however, the absence of Lon protease nearly nullified the BC-mediated repression of SPI-1 genes. Intriguingly, overexpression of RamA repressed the transcription of SPI-1 genes; however, its negative regulation of SPI-1 expression is likely to be independent of the Lon-mediated regulation of SPI-1. These results demonstrated that treatment with sublethal concentrations of BC not only stimulates Salmonella to develop resistance mechanisms against BC, but also influences Salmonella virulence.

Single-cell hemoprotein (heme-SCP) exerts the prebiotic potential to establish a healthy gut microbiota in small pet dogs.

To investigate the effect of the single-cell hemoprotein (heme-SCP) source on animals, a dog-treat (100 g for each dog) harboring 0.2% heme-SCP was manufactured and fed to seven pet dogs (< 10 kg) in a randomized manner (irrespective of owner's feeding style, dogs' health conditions, and staple diets), and the feces before and after the dog-treat diet were analyzed to define the structure of the microbiota. The total bacterial species of the seven dogs showed no difference (564-584), although the bacterial compositions varied significantly. The Firmicutes phylum increased (54.7-73.7%), showing differential species composition before and after heme-SCP intake. Proteobacteria, Bacteroidetes, and Fusobacteria decreased (5.4-3.8%, 32.9-16.8%, and 6.3-3.6%, respectively), which agreed with the previous observation of deliberate feeding. Therefore, it is conceivable that heme-SCP as a prebiotic can shape the gut microbiota regardless of the administration method. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-022-01195-9.

Single-Cell Hemoprotein Diet Changes Adipose Tissue Distributions and Re-Shapes Gut Microbiota in High-Fat Diet-Induced Obese Mice.

We have previously observed that feeding with single-cell hemoprotein (heme-SCP) in dogs (1 g/day for 6 days) and broiler chickens (1 ppm for 32 days) increased the proportion of lactic acid bacteria in the gut while reducing their body weights by approximately 1~2%. To define the roles of heme-SCP in modulating body weight and gut microbiota, obese C57BL/6N mice were administered varied heme-SCP concentrations (0, 0.05, and 0.5% heme-SCP in high fat diet) for 28 days. The heme-SCP diet seemed to restrain weight gain till day 14, but the mice gained weight again later, showing no significant differences in weight. However, the heme-SCP-fed mice had stiffer and oilier bodies compared with those of the control mice, which had flabby bodies and dull coats. When mice were dissected at day 10, the obese mice fed with heme-SCP exhibited a reduction in subcutaneous fat with an increase in muscle mass. The effect of heme-SCP on the obesity-associated dyslipidemia tended to be corroborated by the blood parameters (triglyceride, total cholesterol, and C-reactive protein) at day 10, though the correlation was not clear at day 28. Notably, the heme-SCP diet altered gut microbiota, leading to the proliferation of known anti-obesity biomarkers such as Akkermansia, Alistipes, Oscillibacter, Ruminococcus, Roseburia, and Faecalibacterium. This study suggests the potential of heme-SCP as an anti-obesity supplement, which modulates serum biochemistry and gut microbiota in high-fat diet-induced obese mice.

Corrigendum: Motility increase of Adherent Invasive Escherichia coli (AIEC) induced by a sub-inhibitory concentration of recombinant endolysin LysPA90.

[This corrects the article DOI: 10.3389/fmicb.2022.1093670.].

Analysis of HilC/D-dependent invF promoter expression under different culture conditions.

In Salmonella enterica serovar Typhimurium, many of the genes required for intestinal penetration and invasion of host cells are encoded within the Salmonella pathogenicity island 1 (SPI1). The expression of invF, which is a positive transcriptional activator of SPI1, is controlled by HilA-dependent (invF-1) and HilC/D-dependent (invF-2) promoters. Transcriptional analysis of invF revealed that the invF-2 promoter (P(invF-2)) was not activated when cells were grown in standing culture conditions (which are known to induce SPI1) and that hilD mutation decreased the expression of P(invF-2) only in shaking culture conditions. In the absence of invF-1 promoter (P(invF-1)), P(invF-2) promoted InvF production and sipC expression (which is regulated by InvF) in shaking culture conditions. An analysis of the transcription patterns of plasmids harboring the lacZY reporter gene under various P(invF-2) derivatives with truncations or mutations revealed that the downstream region of the P(invF-2) transcription start site (i.e., +148 to +363) plays a role in repressing P(invF-2) in standing culture and in HilD-dependent activation of P(invF-2) in shaking culture conditions. The expression of invH overlaps with P(invF-2), but they are transcribed in opposite directions. However, invH expression did not influence P(invF-2) activity. This suggests that independent regulation of the two invF promoters allows Salmonella to respond quickly to environmental changes.

Cooperative Interaction between Acid and Copper Resistance in Escherichia coli.

The persistence of pathogenic Escherichia coli under acidic conditions poses a serious risk to food safety, especially in acidic foods such as kimchi. To identify the bacterial factors required for acid resistance, transcriptomic analysis was conducted on an acid-resistant enterotoxigenic E. coli strain and the genes with significant changes in their expression under acidic pH were selected as putative resistance factors against acid stress. These genes included those associated with a glutamatedependent acid resistance (GDAR) system and copper resistance. E. coli strains lacking GadA, GadB, or YbaST, the components of the GDAR system, exhibited significantly attenuated growth and survival under acidic stress conditions. Accordantly, the inhibition of the GDAR system by 3-mercaptopropionic acid and aminooxyacetic acid abolished bacterial adaptation and survival under acidic conditions, indicating the indispensable role of a GDAR system in acid resistance. Intriguingly, the lack of cueR encoding a transcriptional regulator for copper resistance genes markedly impaired bacterial resistance to acid stress as well as copper. Conversely, the absence of YbaST severely compromised bacterial resistance against copper, suggesting an interplay between acid and copper resistance. These results suggest that a GDAR system can be a promising target for developing control measures to prevent E. coli resistance to acid and copper treatments.