ABSTRACT
Lacticaseibacillus rhamnosus Probio-M9 (Probio-M9) is increasingly used as a co-fermentation culture in fermented milk production. Recently, a capsular polysaccharide (CPS)- and exopolysaccharide (EPS)-producing mutant of Probio-M9, HG-R7970-3, was generated by space mutagenesis. This study compared the performance of cow and goat milk fermentation between the non-CPS/-EPS-producing parental strain (Probio-M9) and the CPS/EPS producer (HG-R7970-3), and the stability of products fermented by the two bacteria. Our results showed that using HG-R7970-3 as the fermentative culture could improve the probiotic viable counts, physico-chemical, texture, and rheological properties in both cow and goat milk fermentation. Substantial differences were also observed in the metabolomics profiles between fermented cow and goat milks produced by the two bacteria. Comparing with Probio-M9-fermented cow and goat milks, those fermented by HG-R7970-3 were enriched in a number of flavor compounds and potential functional components, particularly acids, esters, peptides, and intermediate metabolites. Moreover, HG-R7970-3 could improve the post-fermentation flavor retention capacity. These new and added features are of potential to improve the techno-functional qualities of conventional fermented milks produced by Probio-M9, and these differences are likely imparted by the acquired CPS-/EPS-producing ability of the mutant. It merits further investigation into the sensory quality and in vivo function of HG-R7970-3-fermented milks.
Subject(s)
Cultured Milk Products , Lacticaseibacillus rhamnosus , Probiotics , Animals , Female , Cattle , Milk/chemistry , Lacticaseibacillus rhamnosus/genetics , Lacticaseibacillus , Probiotics/chemistry , Fermentation , Bacteria , Goats , Cultured Milk Products/microbiologyABSTRACT
The study of microorganisms in outer space has focused mainly on investigating phenotypic changes in microbial pathogens induced by factors encountered in space. This study aimed to investigate the effect of space exposure on a probiotic bacterium, Lacticaseibacillus rhamnosus Probio-M9. Probio-M9 cells were exposed to space in a spaceflight. Interestingly, our results showed that a substantial proportion of space-exposed mutants (35/100) exhibited a ropy phenotype, characterized by their larger colony sizes and an acquired ability to produce capsular polysaccharide (CPS), compared with the original Probio-M9 or the ground control isolates without space exposure. Whole-genome sequencing analyses on both the Illumina and PacBio platforms revealed a skewed distribution of single nucleotide polymorphisms (12/89 [13.5%]) toward the CPS gene cluster, particularly in the wze (ywqD) gene. The wze gene encodes a putative tyrosine-protein kinase that regulates CPS expression through substrate phosphorylation. Transcriptomics analysis of two space-exposed ropy mutants revealed increased expression in the wze gene relative to a ground control isolate. Finally, we showed that the acquired ropy phenotype (CPS-producing ability) and space-induced genomic changes could be stably inherited. Our findings confirmed that the wze gene directly influences the capacity for CPS production in Probio-M9, and space mutagenesis is a potential strategy for inducing stable physiological changes in probiotics. IMPORTANCE This work investigated the effect of space exposure on a probiotic bacterium, Lacticaseibacillus rhamnosus Probio-M9. Interestingly, the space-exposed bacteria became capable of producing capsular polysaccharide (CPS). Some probiotic-derived CPSs have nutraceutical potential and bioactive properties. They also enhance the survival of probiotics through the gastrointestinal transit and ultimately strengthen the probiotic effects. Space mutagenesis seems to be a promising strategy for inducing stable changes in probiotics, and the obtained high-CPS-yielding mutants are valuable resources for future applications.
ABSTRACT
Space mutation is an efficient tool in microbial breeding. The aim of the present study was to screen out space-induced mutants of Lactobacillus plantarum with potent probiotic properties. The wild-type Lactobacillus plantarum GS18 was subjected to 31 days and 18.5 hr of space flight, in which 13 isolates were selected for analysis. These mutants were assayed for milk fermentation performance, low pH resistance, bile salt tolerance, hydrophobicity, and antimicrobial activity. The 16S rDNA sequencing was applied to identify the stain and compare it with the wild type. Results showed that the isolate L. plantarum SS18-50 had the strongest probiotic properties with no mutation in 16S rRNA sequence compared to the wild type. Specifically, L. plantarum SS18-50 had good milk fermentation performance. The viscosity of fermented milk, acid tolerance, and bile salt tolerance were increased by approximately 10%, 8%, and 9%, respectively (p < .05). The antibacterial activity (Escherichia Coli, Salmonella Typhimurium, and Listeria Monocytogenes) was also increased significantly compared to the wild type (p < .05). This study indicates that L. plantarum SS18-50 has the great potential to serve as a probiotic for dairy products.
ABSTRACT
Objective To evaluate the indeterminate growth mutant of tomato derived by space mutagenesis to provide the basis for selecting and cultivating the molecular markers of tomato growth habit. Methods Fifty 10-mer randomly amplified polymorphic DNA(RAPD) primers were used to examine the polymorphism of M1 and 10-3-2. Their polymorphic fragments were cloned, and then were transferred to SCAR markers. Results Of all the 50 10-mer RAPD primers, 44 primers amplified polymerase chain reaction(PCR) products and 2 primers (S165 and S168) amplified stable reproducible polymorphic products. The molecular weight of the specific amplified products were 300 bp and 1 500 bp respectively, therefore they were named as TRS165300 and TRS1681500 temporarily. And TRS1681500 was transferred into stable sequence characterized amplified region(SCAR) marker and this marker could be a specific genetic marker of this indeterminate growth habit mutant. Conclusion Space mutation can produce mutants at DNA level from the loaded materials. The indeterminate growth mutant of tomato is derived by space mutagenesis which can provide a valuable material for studying the regulation and control of tomato growth habit.
ABSTRACT
Objective To analyze the new breeding of eggplant "HANGQIE-5"(HQ-5) generated by space mutagenesis with RAPD,identify the differential RAPD bands,and try to provide molecular proofs for space mutation breeding.Methods Dry seeds of two eggplants "Tianshuichangqie(TSCQ)" and Longguoyuanqie(LGYQ) were carried by "shenzhou-4" and "shenzhou-3"spaceship.Two mutant lines "TSCQ-MUT-4" and "LGYQ-MUT-4" were selected after four generations of self-cross of TSCQ and LGYQ.A new variety of "HQ-5" was selected by crossing the two lines of "TSCQ-MUT-4" and "LGYQ-MUT-4",which were male and female,respectively.The RAPD reaction system was optimized with orthogonal design and further RAPD analysis was applied.Results The RAPD reaction system was determined as follows: DNA: 40 ng,dNTPs: 7.5 nmol,primer: 10 ng,and rTaq polymerase: 1.25 U.The RAPD results displayed that TSCQ-MUT-4 produced four differential bands compared with its wild type,while LGYQ-MUT-4 produced one,through space flight.Six differential fragments were amplified between HQ-5 and the paternal/maternal.HQ-5 not only shared the common fragments with its parents,but also held some particular ones,which were stably inherited.Conclusion The results indicate that space mutagenesis could cause mutations in DNA of plants,and is helpful to generate a new breeding.
