Kimchi bacteriophages of lactic acid bacteria: population, characteristics, and their role in watery kimchi.

The bacteriophages (phages) in the watery kimchis (Baek-kimchi and Dongchimi) were characterized to determine the phage ecology of lactic acid bacteria (LAB). Kimchi obtained from the Seoul markets had an average of 2.1 log phage particles/mL, corresponding to 28% of the bacterial counts on a log scale. High counts of 5.5-6.5 log particles/mL of phages were noted in the early phase of fermentation (reaching pH 4), and 2.1-3.0 log phage particles/mL were found in the later phase, with some fluctuation in numbers. The LAB hosts changed from Weissella and Leuconostoc to Lactobacillus during Dongchimi fermentation. Fifteen phages, except for those of Lactobacillus, were isolated from diverse strains in the early phase. Five Weissella phages were Podoviridae, and all 10 Leuconostoc phages were Myoviridae. Phages had narrow and different host infection spectra to strains of the same species and high acidic stability. Therefore, the mortality and diversity of LAB during natural kimchi fermentation may be related to the specific phages of the hosts. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10068-021-00930-y.

Acid tolerance and morphological characteristics of five Weissella cibaria bacteriophages isolated from kimchi.

Five bacteriophages were isolated from kimchi with the hosts of two Weissella cibaria and acid-producing bacteria, and characterized for understanding Weissella phage. By transmission electron microscope, фWC51 and фWC52 belonged to the Myoviridae and фWC005, фWC130, and фWC248 belonged to the Podoviridae. One-step growth curves showed that latent periods of bacteriophages ranged from 70 to 90 min and burst sizes ranged from 7 to 195 particles/cell. фWC51 and фWC005 were thermally resistant than the others and those D values were 71 and 34 s at 70 °C. pH stability test at pH 2.0-4.0 showed фWC005 was most stable and the others were also stable at low pH of 3.0. Interestingly, the phages showed two types of morphology and had a high tolerance under acidic condition, therefore, which might cause mortality to the Weissella after middle stage of kimchi fermentation.

Effect of Bacteriophages on Viability and Growth of Co-cultivated Weissella and Leuconostoc in Kimchi Fermentation.

This study aimed to understand the survival and growth patterns of bacteriophage-sensitive Weissella and Leuconostoc strains involved in kimchi fermentation. Dongchimi kimchi was prepared, and Weissella and Leuconostoc were co-cultivated in the dongchimi broth. Weissella cibaria KCTC 3807 growth was accompanied by rapid lysis with an increase in the bacteriophage quantity. Leuconostoc citreum KCCM 12030 followed the same pattern. The bacteriophage-insensitive strains W. cibaria KCTC 3499 and Leuconostoc mesenteroides KCCM 11325 survived longer under low pH as their growth was not accompanied by bacteriophages. The bacteriophage lysate of W. cibaria KCTC 3807 accelerated and promoted the growth of Leuconostoc. Overall, our results show that bacteriophages might affect the viability and population dynamics of lactic acid bacteria during kimchi fermentation.

A Foot-Arch Parameter Measurement System Using a RGB-D Camera.

The conventional method of measuring foot-arch parameters is highly dependent on the measurer's skill level, so accurate measurements are difficult to obtain. To solve this problem, we propose an autonomous geometric foot-arch analysis platform that is capable of capturing the sole of the foot and yields three foot-arch parameters: arch index (AI), arch width (AW) and arch height (AH). The proposed system captures 3D geometric and color data on the plantar surface of the foot in a static standing pose using a commercial RGB-D camera. It detects the region of the foot surface in contact with the footplate by applying the clustering and Markov random field (MRF)-based image segmentation methods. The system computes the foot-arch parameters by analyzing the 2/3D shape of the contact region. Validation experiments were carried out to assess the accuracy and repeatability of the system. The average errors for AI, AW, and AH estimation on 99 data collected from 11 subjects during 3 days were -0.17%, 0.95 mm, and 0.52 mm, respectively. Reliability and statistical analysis on the estimated foot-arch parameters, the robustness to the change of weights used in the MRF, the processing time were also performed to show the feasibility of the system.

Kinematic and kinetic analyses of novice running in dress shoes and running shoes.

The purpose of the study was to investigate how novice runners adjust their lower extremities in heel-toe running while they wear dress shoes and running shoes. Ten novice male runners repeatedly ran across a force plate at 4 m/s in each type of shoes. Joint kinematics and kinetics, vertical ground reaction force, and utilized coefficient of friction during the stance phase were quantified. The results obtained showed no differences in impact peaks, stance time, stride length and joint kinematics. However, dorsiflexion moment was significantly greater with dress shoes (407 Nm) compared to that with running shoes (304 Nm; p<0.05). Compared to the runners in running shoes (0.23), the runners in dress shoes (0.20) achieved a significantly lower utilized coefficient of friction ( p<0.05). When running in dress shoes, novice runners tended to use better a dorsiflexion moment than when running in running shoes. This adaptation appears to minimize the chances of slipping at the moment of heel strike.