Search Results (6)

The mutualistic relationship between Streptococcus thermophilus (S. thermophilus) and L. delbrueckii subsp. bulgaricus (L. bulgaricus) is responsible for milk coagulation, gel formation, and the flavour of yogurt. Under set-style yogurt processing conditions, the performance of a mixed culture composed of these species depends on key technological parameters such as the capacity for acidification and proteolytic activity. This study aimed to determine the extent of phenotypic diversity by comparing the key traits of acidification and proteolytic activity among isolates found in yogurt starter cultures. Seventy-two isolates from three industrial starter cultures were ranked by either their fast or slow acidification activity (time to reach pH 4.6, 16 h), proteolytic activity, cell envelope proteinase (CEP) activity, redox potential and titratable acidity. The integration of multiple phenotype measures by hierarchical clustering and non-metric dimensional scaling (NMDS) clustered groups of isolates by multifactor similarity. A significant difference (p-value < 0.05) was observed between the clusters regarding redox potential and the proteolytic activity of both S. thermophilus and L. bulgaricus. The integration of multiple phenotypes points to the diversification that may have occurred over repeated culturing of yogurt starter bacteria. The phenotypic diversity may explain the divergence in starter performance and be used to refine the formulation of new starter cultures. Future work will investigate the correlation between the activity of specific enzymes based on the phenotype to explain the separation between the fast and slow acidification of isolates. Full article

The specificity of phages and their ability to evolve and overcome bacterial resistance make them potentially useful as adjuncts in the treatment of antibiotic-resistant bacterial infections. The goal of this study was to mimic a natural grouping of phages of interest and to evaluate the nature of their proliferation dynamics with bacteria. We have, for the first time, transferred naturally occurring phage groups directly from their sources of isolation to in vitro and identified 13 P. aeruginosa and 11 K. pneumoniae phages of 18 different genera, whose host range was grouped as 1.2–17%, 28–48% and 60–87%, using a large collection of P. aeruginosa (n = 102) and K. pneumoniae (n = 155) strains carrying different virulence factors and phage binding receptors. We introduced the interpretation model curve for phage liquid culturing, which allows easy and quick analysis of bacterial and phage co-proliferation and growth of phage-resistant mutants (PRM) based on qualitative and partially quantitative evaluations. We assayed phage lytic activities both individually and in 14 different cocktails on planktonic bacterial cultures, including three resistotypes of P. aeruginosa (PAO1, PA14 and PA7) and seven K. pneumoniae strains of different capsular serotypes. Based on the results, the natural phage cocktails designed and tested in this study largely performed well and inhibited PRM growth either synergistically or in proto-cooperation. This study contributes to the knowledge of phage behavior in cocktails and the formulation of therapeutic phage preparations. The paper also provides a detailed description of the methods of working with phages. Full article

The occurrence of Fusarium Head Blight (FHB) mycotoxins in wheat grains is a major threat to global food safety and security. Humans and animals are continuously being exposed to Fusarium mycotoxins such as deoxynivalenol (DON) and its acetylated derivatives 3ADON and 15ADON through the ingestion of contaminated food or grain-based diet. In this study, a host-specific mycoparasite biocontrol agent (BCA), Sphaerodes mycoparasitica, significantly reduced FHB mycotoxin occurrence in harvested wheat grains from Fusarium graminearum 3ADON chemotype infected plants in greenhouse. Four genotypes of wheat, two common wheat and two durum wheat cultivars with varying FHB resistance levels were used in this study. Principal Coordinate Analysis (PCoA) using Illumina ITS sequences depicted beta diversity changes in Fusarium species indicating that both plant cultivar and BCA treatments influenced the Fusarium species structure and mycotoxin occurrence in grains. Fusarium graminearum complex (cluster A), F. avenaceum and F. acuminatum (cluster B), and F. proliferatum (cluster C) variants were associated with different FHB mycotoxins based on LC-MS/MS analyses. The predominant FHB mycotoxins measured were DON and its acetylated derivatives 3ADON and 15ADON. The BCA reduced the occurrence of DON in grains of all four cultivars (common wheat: 1000–30,000 µg·kg⁻¹.; durum wheat: 600–1000 µg·kg⁻¹) to levels below the Limit of Quantification (LOQ) of 16 µg·kg⁻¹. A relatively higher concentration of DON was detected in the two common wheat genotypes when compared to the durum wheat genotype; however, the percentage reduction in the wheat genotypes was greater, reaching up to 99% with some S. mycoparasitica treatments. Similarly, a higher reduction in DON was measured in susceptible genotypes than in resistant genotypes. This study’s findings underscore the potential of a Fusarium-specific S. mycoparasitica BCA as a safe and promising alternative that can be used in conjunction with other management practices to minimize FHB mycotoxins in cereal grain, food and feed intended for human and animal consumption. Full article

Over the past century, the economically devastating Fusarium Head Blight (FHB) disease has persistently ravished small grain cereal crops worldwide. Annually, losses globally are in the billions of United States dollars (USD), with common bread wheat and durum wheat accounting for a major portion of these losses. Since the unforgettable FHB epidemics of the 1990s and early 2000s in North America, different management strategies have been employed to treat this disease. However, even with some of the best practices including chemical fungicides and innovative breeding technological advances that have given rise to a spectrum of moderately resistant cultivars, FHB still remains an obstinate problem in cereal farms globally. This is in part due to several constraints such as the Fusarium complex of species and the struggle to develop and employ methods that can effectively combat more than one pathogenic line or species simultaneously. This review highlights the last 100 years of major FHB epidemics in the US and Canada, as well as the evolution of different management strategies, and recent progress in resistance and cultivar development. It also takes a look at protocooperation between specific biocontrol agents and cereal genotypes as a promising tool for combatting FHB. Full article

The present study contributes to the knowledge of epibionts recorded on sea turtles that nested on a beach in the South Pacific of Mexico. A total of 125 Lepidochelys olivacea turtles nested on Llano Real beach, Guerrero, Mexico, were examined. We collected 450 conspicuous organisms from 8 species from 43 turtles. The corresponding data analysis was carried out to obtain the relative abundance, the relationship between turtle sizes and the presence of organisms, the similarity of species between the sampling months, and the interspecific relationships between the epibionts and the turtles observed. Chelonibia testudinaria was the most abundant species, while Remora remora was the least abundant species. The turtles were divided into six body sections, with the greatest abundance of these organisms located in the head–neck section of turtles, and there was a significant difference in the size of the turtles that presented epibionts and those that did not. C. testudinaria showed greater similarity between sampling months, and the interspecific relationships recorded were commensalism, parasitism, amensalism, and protocooperation. This research contributes the first record of epibionts in L. olivacea nesting in Guerrero, Mexico. Full article

A great number of factors can influence milk fermentation for yoghurt production such as fermentation conditions, starter cultures and milk characteristics. It is important for dairy companies to know the best combinations of these parameters for a controlled fermentation and for the desired qualities of yoghurt. This study investigates the use of a ¹H-NMR metabolomics approach to monitor the changes in milk during fermentation from time 0 to 24 h, taking samples every hour in the first 8 h and then at the end-point at 24 h. Three different starter cultures (L. delbrueckii ssp. bulgaricus, S. thermophilus and their combination) were used and two different heat treatments (99 or 105 °C) were applied to milk. The results clearly show the breakdown of proteins and lactose as well as the concomitant increase in acetate, lactate and citrate during fermentation. Formate is found at different initial concentrations depending on the heat treatment of the milk and its different time trajectory depends on the starter cultures: Lactobacillus cannot produce formate, but needs it for growth, whilst Streptococcus is able to produce formate from pyruvate, therefore promoting the symbiotic relationship between the two strains. On the other hand, Lactobacillus can hydrolyze milk proteins into amino acids, enriching the quality of the final product. In this way, better insight into the protocooperation of lactic acid bacteria strains and information on the impact of a greater heat treatment in the initial matrix were obtained. The global chemical view on the fermentations provided using NMR is key information for yoghurt producers and companies producing starter cultures. Full article