Bacteria Community Analysis by Quantitative Real-Time PCR of Fermenting Wax Gourd and its Changes of Organic Acids

Lactic acid bacteria as an eco-friendly approach in plant production: Current state and prospects

Since the late nineteenth century, the agricultural sector has experienced a tremendous increase in chemical use in response to the growing population. Consequently, the intensive and indiscriminate use of these substances caused serious damage on several levels, including threatening human health, disrupting soil microbiota, affecting wildlife ecosystems, and causing groundwater pollution. As a solution, the application of microbial-based products presents an interesting and ecological restoration tool. The use of Plant Growth-Promoting Microbes (PGPM) affected positive production, by increasing its efficiency, reducing production costs, environmental pollution, and chemical use. Among these microbial communities, lactic acid bacteria (LAB) are considered an interesting candidate to be formulated and applied as effective microbes. Indeed, these bacteria are approved by the European Food Safety Authority (EFSA) and Food and Drug Administration (FDA) as Qualified Presumption of Safety statute and Generally Recognized as Safe for various applications. To do so, this review comes as a road map for future research, which addresses the different steps included in LAB formulation as biocontrol, bioremediation, or plant growth promoting agents from the isolation process to their field application passing by the different identification methods and their various uses. The plant application methods as well as challenges limiting their use in agriculture are also discussed.

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.

A novel real-time PCR assay for the specific identification and quantification of Weissella viridescens in blood sausages

Weissella viridescens has been identified as one of the lactic acid bacteria (LAB) responsible for the spoilage of "morcilla de Burgos". In order to identify and quantify this bacterium in "morcilla de Burgos", a new specific PCR procedure has been developed. The primers and Taqman probe were designed on the basis of a sequence from the gene recN. To confirm the specificity of the primers, 77 strains from the genera Carnobacterium, Enterococcus, Lactobacillus, Leuconostoc, Pediococcus, Streptococcus, Vagococcus and Weissella were tested by conventional PCR. The specificity of the primers and the correct functioning of the probe was confirmed by performing real-time PCR (qPCR) with 21 W. viridescens strains and 27 strains from other LAB genera. The levels of detection and quantification for the qPCR procedure proposed herein were determined for a pure culture of W. viridescens CECT 283(T) and for "morcilla de Burgos" artificially inoculated with this species. The primers were specific for W. viridescens, with only one product of 91 bp being observed for this species. Similarly, the qPCR reactions were found to be specific, amplifying at a mean CT of 15.0±0.4 only for W. viridescens strains. The limit of detection (LOD) and quantification (LOQ) for this procedure was established in 0.082 pg for genomic DNA from W. viridescens. With regard to the artificially inoculated "morcilla", the limit of quantification was established in 80 CFU/reaction and the limit of detection in 8 CFU/reaction. Consequently, the qPCR developed herein can be considered to be a good, fast, simple and accurate tool for the specific detection and quantification of W. viridescens in meat samples.