Glycogen plays a key role in survival of Salmonella Typhimurium on dry surfaces and in low-moisture foods.

Salmonella enterica is known to survive in desiccate environments and is often associated with low-moisture foods (LMFs). In this work, S. Typhimurium ATCC 14028 was found to survive better by achieving the least reductions (3.17 ± 0.20 Log CFU reduction) compared to S. Tennessee ATCC 10722 (3.82 ± 0.13 Log CFU reduction) and S. Newport ATCC 6962 (6.03 ± 0.36 Log CFU reduction) after 30 days on surfaces with a relative humidity of 49% at ambient temperature. A metabolomic analysis revealed that S. Typhimurium was still active in energy metabolism after 24 h in the desiccate environment and glycogen, an energy reserve, was drastically reduced. We followed up on the glycogen levels over 30 days and found indeed a sharp decline on the first day. However, the glycogens detected on day 7 were significantly higher (P < 0.05) and thereafter remained stable above the original levels until day 30. The expression levels of both glycogen anabolism- and catabolism-related genes (csrA, glgA, glgC, glgX) were significantly up-regulated at all tested points (P < 0.05). The glgA and glgC insertion mutants displayed weaker survivability on both dry surfaces and in representative LMFs (flour and milk powder) compared to the wild-type strain. This work highlights the role of glycogen during different periods of desiccation, which may bring novel insight into mitigating Salmonella by disrupting glycogen metabolism.

Metabolomics investigation of global responses of Cronobacter sakazakii against common sanitizing in infant formula processing environments.

Cronobacter sakazakii, an opportunistic bacterium, has raised a serious outbreak in powdered infant formula recent years. In this work, four sanitizing strategies used during infant formula processing, including chlorine, quaternary ammonium chloride (QAC), 60 °C heating, and malic acid (MA), were utilized against C. sakazakii among planktonic, air-dried (A), and air-dried & washed (AW) state, followed by an exploration of the metabolic responses induced by these treatments via a dual-platform metabolomics analysis with the ultra-high performance liquid chromatography-mass spectrometry and nuclear magnetic resonance. In the planktonic state, MA was the most effective in inhibiting bacterial growth, followed by chlorine, QAC, and 60 °C heating. Under A state, the efficacy of heating improved considerably, compared to that in the planktonic state, and remained unaltered under AW state. Chlorine and QAC were ineffective to control bacterial growth under A state, but their efficacy rose under AW state. Furthermore, the metabolomic analysis revealed chlorine induces amino acids catabolism, membrane lysis, and depression in carbohydrate and nucleotide metabolism in both planktonic and AW states, while the initiation of antioxidation mechanism was only found under AW state. Although the metabolic change caused by QAC in the planktonic state was similar to chlorine, the accumulation of osmoprotectant and membrane phospholipids within the AW cells reflected the effort to restore intracellular homeostasis upon QAC. Heating was characterized by considerable amino acid anabolism, along with mildly perturbed carbohydrate and nucleotide metabolism for heat shock protein preparation in both states. Lastly, MA promoted amino acid-dependent acid resistance under the planktonic state, and the regulation of antioxidation and osmoprotection under AW state. The metabolomics study elucidated the intracellular perturbation induced by common sanitizing, as well as the bacterial response, which provides insights for novel sanitization development.

Dual-Species Biofilms Formed by Escherichia coli and Salmonella Enhance Chlorine Tolerance.

In this research, mono- and dual-species biofilms of Escherichia coli (O45:H2 and O121:H19) and Salmonella enterica serovar Typhimurium formed on stainless-steel coupons were treated with 100 mg/L NaClO for 1 min. Confocal laser scanning microscopy (CLSM) was applied to investigate the spatial structural dynamics of mono- and dual-species biofilms, and nuclear magnetic resonance (NMR) spectroscopy was employed to further investigate their metabolic responses toward chlorine. CLSM results indicated that mixed-species biofilms (total biovolume, 148,000 to 167,000 µm3) stimulated the growth of biomass 2 to 6 times that of single-species biofilms. Upon chlorine treatment, E. coli O45 and S. Typhimurium achieved less reduction (P < 0.05) when coexisting in mixed biofilms (0.70 and 1.17 log CFU/coupon reductions, respectively) compared with their corresponding single-species biofilms (1.97 and 2.01 log CFU/coupon reductions, respectively), while for E. coli O121, more reduction (P < 0.05) was achieved in a mixed biofilm (1.37 log CFU/coupon reductions) compared with its single-species biofilm (0.59 log CFU/coupon reductions). Moreover, NMR results suggested that the increase of putrescine (antioxidation regulator) and the decrease of glucose (enhanced glycolysis for energy replenishment) might contribute to the improved chlorine tolerance in mixed biofilms. Overall, dual-species biofilms promoted biofilm growth and their chlorine tolerance. This study improved our knowledge of the metabolic difference of single- and mixed-species biofilms of E. coli and Salmonella to chlorine sanitization and raised an urgency to investigate the effectiveness of common disinfectants against multispecies consortia. IMPORTANCE Outbreaks of Escherichia coli and Salmonella in food might be associated with the cross-contamination of biofilms on food-contact surfaces. The knowledge of the sanitization of mono-species biofilm on the food-contact surface is well established, while mixed-species biofilm occurs more naturally, which could profoundly affect the efficacy of sanitizer. Therefore, this research aims to evaluate the efficacy of using chlorine against single- and dual-species biofilms of E. coli and Salmonella along with the underlying bacterial metabolic responses. The responses of a mixed biofilm of E. coli and Salmonella to chlorine sanitization were clarified, providing insights to develop a targeted and green sanitization strategy against specific pathogens by perturbing their most susceptible metabolism pathway without sanitizer residue.

Effect of chlorine sanitizer on metabolic responses of Escherichia coli biofilms "big six" during cross-contamination from abiotic surface to sponge cake.

The effect of chlorine on Escherichia coli biofilm O157:H7 are well established; however, the effect on biofilm adhesion to food as well as the six emerging E. coli serotypes ("big six") have not been fully understood. Chlorine sanitization with 1-min 100 mg/L was applied against seven pathogenic E. coli (O111, O121:H19, O45:H2, O26:H11, O103:H11, O145, and O157:H7) biofilms on high-density polyethylene (HDPE) and stainless steel (SS) coupons, respectively. Using sponge cake as a food model, the adhesion behavior was evaluated by comparison of bacteria transfer rate before and after treatment. Besides, the metabolic profiles of biofilms were analyzed by nuclear magnetic resonance (NMR) spectrometer. A significant decrease in transfer rate (79% decline on SS and 33% decline on HDPE) was recorded as well as the distinctive pattern between SS and HDPE coupons was also noticed, with a low population (6-7 log CFU/coupon) attached and low survivals (0-3 log CFU/coupon) upon chlorine on SS, while high population (7-8 log CFU/coupon) attached and high survivals (5-7 log CFU/coupon) on HDPE. Moreover, O121:H19 and O26:H11 demonstrated the highest resistance to chlorine with the least metabolic status and pathways affected. O103:H11, O145, and O111 followed similar metabolic patterns on both surfaces. Distinct metabolic patterns were found in O45:H2 and O157:H7, where the former had more affected metabolic status and pathways on SS but less on HDPE, whereas the latter showed an opposite trend. Overall, a potential contamination source of STEC infection in flour products was demonstrated and metabolic changes induced by chlorine were revealed by NMR-based metabolomics, which provides insights to avoid "big six" biofilms contamination in food.

Autofocusing self-imaging: symmetric Pearcey Talbot-like effect.

The Talbot-like effect of symmetric Pearcey beams (SPBs) is presented numerically and experimentally in the free space. Owing to the Talbot-like effect, the SPBs have the property of periodic, multiple autofocusing and self-healing. Meanwhile, the focusing positions and focusing times of SPBs are controlled by the beam shift factor and the distribution factors. Furthermore, the beam shift factor can also affect the Talbot-like effect and the Talbot period. It is believed that the results can diversify the application of the Talbot effect.

Propagation dynamics of the odd-Pearcey Gaussian beam in a parabolic potential.

In this paper, the propagation properties of the odd-Pearcey Gaussian beam (OPGB) in a parabolic potential are investigated analytically and numerically. Except for the auto-focusing at the focal plane, the OPGB performs a weak off-axis focusing unexpectedly. The focusing distance and the focal intensity can be adjusted by choosing an appropriate parabolic parameter. Also, the Poynting vector of the OPGB is demonstrated. In addition, we investigate the radiation forces of the OPGB and find that the trapping points can be generated during propagation.

Accelerating trajectory manipulation of symmetric Pearcey Gaussian beam in a uniformly moving parabolic potential.

We derive analytical solutions that describe the one-dimensional displaced and chirped symmetric Pearcey Gaussian beam in a uniformly moving parabolic potential. The multiple effective manipulations of the beam, which are originated from the diverse configurations of the dynamic parabolic potential, are demonstrated. On the whole, the accelerating trajectory can transform into a linear superposition form of the oblique straight line and the simple harmonic motion. Meanwhile, we discuss the further modulation of the accelerating trajectory characteristics such as slope, amplitude and phase shift. Additionally, the extension into a two-dimensional scenario is also proposed. Our results theoretically improve the practical value of the Pearcey beam, and lead to potential applications in trajectory manipulation and particle manipulation.

Symmetric Pearcey Gaussian beams.

In this Letter, a new, to the best of our knowledge, type of autofocusing and symmetric beam arisen from two quartic spectral phases is introduced in theory and experiment. The symmetric Pearcey Gaussian beam (SPGB), formed with a Gaussian term and two multiplying Pearcey integrals, processes a focusing intensity approximately 1.32 times stronger than the intensity of the symmetric Airy beam. Its four off-axis main lobes split into four bending trajectories symmetrically after focusing. The rectangular intensity distribution and the focal length of the SPGB can be adjusted by two kinds of distribution factors. Additionally, the vortex-guiding property of the beam is demonstrated by embedding an off-axis vortex into the SPGB, which can be applied in particle guiding.

Propagation properties and radiation forces of the Hermite-Gaussian vortex beam in a medium with a parabolic refractive index.

In this paper, an analytical expression with a triple sum of the Hermite-Gaussian vortex beam (HGVB) propagating in a medium with a parabolic transverse spatial distribution of the refractive index is carried out. The intensity, phase, Poynting vector, and angular momentum of the HGVB are demonstrated analytically. The parabolic parameter, orders of the HGVB, and vortex topological charge affect the propagation properties, respectively. Also, the Poynting vector and angular momentum of the HGVB are shown so that we can further discover the properties. Furthermore, radiation forces are used to demonstrate the optical trapping ability of the HGVB, and several trapping positions are formed by the beam during propagation.

Auto-focusing and self-healing of symmetric odd-Pearcey Gauss beams.

In this study, a new, to the best of our knowledge, form of odd-Pearcey Gauss beams with peculiar characteristics is presented. Compared with the Pearcey beam, the odd-Pearcey Gauss beam is symmetrical about the origin. At the initial stages, the odd-Pearcey Gauss beam propagates with a main central lobe and some residual spots that autofocus to the center, and then splits into two off-axis parabolic lobes after the autofocus finishes. Furthermore, we also introduce the soft well function to investigate the propagation profiles of the odd-Pearcey Gauss beams passing through it with different calibers and discuss the influence of the Gaussian waist width towards the focal distance and the propagation form of the odd-Pearcey Gauss beam. We also enumerate some potential and possible applications based on its peculiar characteristics.

Compound phenotype of osteogenesis imperfecta and Ehlers-Danlos syndrome caused by combined mutations in COL1A1 and COL5A1.

Osteogenesis imperfecta (OI) is an inherited connective tissue disorder with a broad clinical spectrum that can overlap with Ehlers-Danlos syndrome (EDS). To date, patients with both OI and EDS have rarely been reported. In the present study, we investigated a family with four members, one healthy individual, one displaying OI only, and two displaying the compound phenotype of OI and EDS, and identified the pathogenic mutations. Whole exome sequencing was applied to the proband and her brother. To verify that the mutations were responsible for the pathogenesis, conventional Sanger sequencing was performed for all members of the family. We identified a known COL1A1 (encoding collagen type I α 1 chain) mutation (c.2010delT, p.Gly671Alafs*95) in all three patients (the proband, her brother, and her mother) in this family, but also a novel heterozygous COL5A1 (encoding collagen type V α 1 chain) mutation (c.5335A>G, p.N1779D) in the region encoding the C-terminal propeptide domain in the proband and her mother, who both had the compound phenotype of OI and EDS. The results of the present study suggested that the proband and her mother presented with the compound OI-EDS phenotype caused by pathogenic mutations in COL5A1 and COL1A1.