Microbial interactions shape cheese flavour formation.

Cheese fermentation and flavour formation are the result of complex biochemical reactions driven by the activity of multiple microorganisms. Here, we studied the roles of microbial interactions in flavour formation in a year-long Cheddar cheese making process, using a commercial starter culture containing Streptococcus thermophilus and Lactococcus strains. By using an experimental strategy whereby certain strains were left out from the starter culture, we show that S. thermophilus has a crucial role in boosting Lactococcus growth and shaping flavour compound profile. Controlled milk fermentations with systematic exclusion of single Lactococcus strains, combined with genomics, genome-scale metabolic modelling, and metatranscriptomics, indicated that S. thermophilus proteolytic activity relieves nitrogen limitation for Lactococcus and boosts de novo nucleotide biosynthesis. While S. thermophilus had large contribution to the flavour profile, Lactococcus cremoris also played a role by limiting diacetyl and acetoin formation, which otherwise results in an off-flavour when in excess. This off-flavour control could be attributed to the metabolic re-routing of citrate by L. cremoris from diacetyl and acetoin towards α-ketoglutarate. Further, closely related Lactococcus lactis strains exhibited different interaction patterns with S. thermophilus, highlighting the significance of strain specificity in cheese making. Our results highlight the crucial roles of competitive and cooperative microbial interactions in shaping cheese flavour profile.

Enhancing the Sweetness of Yoghurt through Metabolic Remodeling of Carbohydrate Metabolism in Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.

UNLABELLED: Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus are used in the fermentation of milk to produce yoghurt. These species normally metabolize only the glucose moiety of lactose, secreting galactose and producing lactic acid as the main metabolic end product. We used multiple serial selection steps to isolate spontaneous mutants of industrial strains of S. thermophilus and L. delbrueckii subsp. bulgaricus that secreted glucose rather than galactose when utilizing lactose as a carbon source. Sequencing revealed that the S. thermophilus strains had mutations in the galKTEM promoter, the glucokinase gene, and genes encoding elements of the glucose/mannose phosphotransferase system (PTS). These strains metabolize galactose but are unable to phosphorylate glucose internally or via the PTS. The L. delbrueckii subsp. bulgaricus mutants had mutations in genes of the glucose/mannose PTS and in the pyruvate kinase gene. These strains cannot grow on exogenous glucose but are proficient at metabolizing internal glucose released from lactose by ß-galactosidase. The resulting strains can be combined to ferment milk, producing yoghurt with no detectable lactose, moderate levels of galactose, and high levels of glucose. Since glucose tastes considerably sweeter than either lactose or galactose, the sweetness of the yoghurt is perceptibly enhanced. These strains were produced without the use of recombinant DNA technology and can be used for the industrial production of yoghurt with enhanced intrinsic sweetness and low residual levels of lactose. IMPORTANCE: Based on a good understanding of the physiology of the lactic acid bacteria Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, we were able, by selecting spontaneously occurring mutants, to change dramatically the metabolic products secreted into the growth medium. These mutants consume substantially more of the lactose, metabolize some of the galactose, and secrete the remaining galactose and most of the glucose back into the milk. This allows production of yoghurt with very low lactose levels and enhanced natural sweetness, because humans perceive glucose as sweeter than either lactose or galactose.

Outcomes and hospital admissions during long-term support with a HeartMate II.

OBJECTIVES: Continuous-flow left ventricular assist devices like the HeartMate II (HMII) improves survival in severe heart failure but little is known about the incidence and causes of hospitalizations during long-term support which was evaluated in this study. DESIGN: Observational follow-up study comprising all patients who received a HMII at our institution either as bridge-to-transplantation (BTT) or destination therapy (DT). All patients were followed from HMII implantation to transplantation, device explantation, death, or May 2015. RESULTS: The HMII was implanted in 66(44 BTT, 22 DT) patients with a median (range) duration of support since implantation of 329(2-2707) days with 260(2-1080) days in the BTT group and 608(6-2707) days in the DT group. Thirty-day mortality was 12% and one-year survival 76%, comparable for DT and BTT. Among 56 (19 DT and 37 BTT) patients discharged alive with a HMII there were 161 hospital readmissions during a follow-up of 336(37-2682) days corresponding to a hospitalization rate of 1.3(0-19) per patient year and with a length of stay of 5(2-72) days per admission. Most frequent cause of readmission was infections (29%). A history of atrial fibrillation was the only independent factor associated with increased readmission rates. CONCLUSIONS: Our single-center study demonstrated encouraging survival following HMII implantation. Hospital readmissions were frequent, mostly of short duration, mainly due to infections and increased in patients with atrial fibrillation.

Exposure of juvenile guppies to three antiandrogens causes demasculinization and a reduced sperm count in adult males.

It has been thoroughly established that the fungicide vinclozolin and the persistent DDT metabolite p,p'-DDE, can function as antiandrogens in mammals in a manner similar to the therapeutic antiandrogen flutamide. In mammals, these chemicals bind the androgen receptor and prevent the transcription of the associated genes causing abnormal sexual development and demasculinization. There are few similar studies in fish and so far it has not been demonstrated that these chemicals have any antiandrogenic effects in this group. In the present study, juvenile guppies (Poecilia reticulata) were fed sublethal doses of vinclozolin, p,p'-DDE or flutamide from birth to adulthood. At sexual maturity, we measured a suite of male sexual characteristics that are known to be under androgen control. All three chemicals caused a reduction in the orange display coloration, inhibited gonopodium development, reduced the sperm count and suppressed courtship behaviour, in a manner consistent with antiandrogen action. Only the gonodosomatic index was unaffected by the treatments. In addition, the three chemicals skewed the sex ratio at adulthood and caused delayed maturation. The altered characters are all considered to be important for male mating success and their impairment indicates that antiandrogens may seriously compromise male reproductive fitness.