Munk and Riley revisited: Nutrient diffusion transport and rates of phytoplankton growth

Although phytoplankton nutrient uptake rates are controlled primarily by biological properties of the organism and nutrient concentration, diffusion transport of nutrient to the organism through the medium in which the organism is immersed can influence uptake rates. The original ideas of Munk and Riley on control of nutrient uptake by diffusion transport are recast in terms of present knowledge of the interaction of diffusion transport and biological control of uptake rates...

Toxic binding of cupric ion by marine phytoplankton

The data presented by Gavis et al. (1981, J. Mar. Res., 39, 315–333) for the specific growth rate of phytoplankton in nutrient replete medium as a function of cupric ion activity can be described quantitatively by equations that relate the equilibrium binding of cupric ions to a cell receptor site. Statistically significant conditional binding constants could be estimated from the data for at least eight clones among three species. One clone could bind only one cupric ion per site. The others could bind a maximum of two cupric ions per site. For one of these clones K1 \u3e K2. For the remaining six K2 \u3e K1. For three clones K2 was so much larger than K1, that only their product β2 could be determined. Values of K1 ranged between 8.6 × 108 and 5.7 x 1010, values of K2 ranged between 3.1 x 108 and 1.9 × 1010, while those of β2 ranged between 3.5 × 1018 and 3.8 × 1020

Cupric ion activity and the growth of phytoplankton clones isolated from different marine environments

The responses to {Cu++} (free cupric ion activity) of 24 clones of 11 species of marine phytoplankton in 4 algal classes were studied in a Cu-Tris buffered medium with a fluorometric method of measuring acclimated growth rates…

Fecal microbiota transplant from a rational stool donor improves hepatic encephalopathy: A randomized clinical trial

Recurrent hepatic encephalopathy (HE) is a leading cause of readmission despite standard of care (SOC) associated with microbial dysbiosis. Fecal microbiota transplantation (FMT) may improve dysbiosis; however, it has not been studied in HE. We aimed to define whether FMT using a rationally derived stool donor is safe in recurrent HE compared to SOC alone. An open-label, randomized clinical trial with a 5-month follow-up in outpatient men with cirrhosis with recurrent HE on SOC was conducted with 1:1 randomization. FMT-randomized patients received 5 days of broad-spectrum antibiotic pretreatment, then a single FMT enema from the same donor with the optimal microbiota deficient in HE. Follow-up occurred on days 5, 6, 12, 35, and 150 postrandomization. The primary outcome was safety of FMT compared to SOC using FMT-related serious adverse events (SAEs). Secondary outcomes were adverse events, cognition, microbiota, and metabolomic changes. Participants in both arms were similar on all baseline criteria and were followed until study end. FMT with antibiotic pretreatment was well tolerated. Eight (80%) SOC participants had a total of 11 SAEs compared to 2 (20%) FMT participants with SAEs (both FMT unrelated; P = 0.02). Five SOC and no FMT participants developed further HE (P = 0.03). Cognition improved in the FMT, but not the SOC, group. Model for End-Stage Liver Disease (MELD) score transiently worsened postantibiotics, but reverted to baseline post-FMT. Postantibiotics, beneficial taxa, and microbial diversity reduction occurred with Proteobacteria expansion. However, FMT increased diversity and beneficial taxa. SOC microbiota and MELD score remained similar throughout. Conclusion: FMT from a rationally selected donor reduced hospitalizations, improved cognition, and dysbiosis in cirrhosis with recurrent HE. Keywords: Cirrhosis; Dysbiosis; Hospitalizations; Metabolomics; Stroop Ap