Composition regulates dissolved organic matter adsorption onto iron (oxy)hydroxides and its competition with phosphate: Implications for organic carbon and phosphorus immobilization in lakes.

Dissolved organic matter (DOM) is a heterogeneous pool of compounds and exhibits diverse adsorption characteristics with or without phosphorous (P) competition. The impacts of these factors on the burial and mobilization of organic carbon and P in aquatic ecosystems remain uncertain. In this study, an algae-derived DOM (ADOM) and a commercially available humic acid (HA) with distinct compositions were assessed for their adsorption behaviors onto iron (oxy)hydroxides (FeOx), both in the absence and presence of phosphate. ADOM contained less aromatics but more protein-like and highly unsaturated structures with oxygen compounds (HUSO) than HA. The adsorption capacity of FeOx was significantly greater for ADOM than for HA. Protein-like and HUSO compounds in ADOM and humic-like compounds and macromolecular aromatics in HA were preferentially adsorbed by FeOx. Moreover, ADOM demonstrated a stronger inhibitory effect on phosphate adsorption than HA. This observation suggests that the substantial release of autochthonous ADOM by algae could elevate internal P loading and pose challenges for the restoration of restore eutrophic lakes. The presence of phosphate suppressed the adsorption of protein-like compounds in ADOM onto FeOx, resulting in an increase in the relative abundance of protein-like compounds and a decrease in the relative abundance of humic-like compounds in post-adsorption ADOM. In contrast, phosphate exhibited no discernible impact on the compositional fractionation of HA. Collectively, our results show the source-composition characters of DOM influence the immobilization of both DOM and P in aquatic ecosystems through adsorption processes. The preferential adsorption of proteinaceous compounds within ADOM and aromatics within HA highlights the potential for the attachment with FeOx to diminish the original source-specific signatures of DOM, thereby contributing to the shared DOM characteristics observed across diverse aquatic environments.

Enameloid-bound δ15 N reveals large trophic separation among Late Cretaceous sharks in the northern Gulf of Mexico.

The nitrogen isotopic composition (15 N/14 N ratio, or δ15 N) of enameloid-bound organic matter (δ15 NEB ) in shark teeth was recently developed to investigate the biogeochemistry and trophic structures (i.e., food webs) of the ancient ocean. Using δ15 NEB , we present the first nitrogen isotopic evidence for trophic differences between shark taxa from a single fossil locality. We analyze the teeth of four taxa (Meristodonoides, Ptychodus, Scapanorhynchus, and Squalicorax) from the Late Cretaceous (83-84 Ma) Trussells Creek site in Alabama, USA, and compare the N isotopic findings with predictions from tooth morphology, the traditional method for inferring shark paleo-diets. Our δ15 NEB data indicate two distinct trophic groups, with averages separated by 6.1 ± 2.1‰. The lower group consists of Meristodonoides and Ptychodus, and the higher group consists of Scapanorhynchus and Squalicorax (i.e., lamniforms). This δ15 NEB difference indicates a 1.5 ± 0.5 trophic-level separation between the two groups, a finding that is in line with paleontological predictions of a higher trophic level for these lamniforms over Meristodonoides and Ptychodus. However, the δ15 NEB of Meristodonoides is lower than suggested by tooth morphology, although consistent with mechanical tests suggesting that higher trophic-level bony fishes were not a major component of their diet. Further, δ15 NEB indicates that the two sampled lamniform taxa fed at similar trophic levels despite their different inferred tooth functions. These two findings suggest that tooth morphology alone may not always be a sufficient indicator of dietary niche. The large trophic separation revealed by the δ15 NEB offset leaves open the possibility that higher trophic-level lamniforms, such as those measured here, preyed upon smaller, lower trophic-level sharks like Meristodonoides.

Invasive Listeriosis in End-Stage Kidney Disease (ESKD) Patients Receiving Long-Term Dialysis: A 21-Year Case Series.

Background: Listeriosis is caused by the facultative anaerobic bacterium Listeria monocytogenes. Infection from Listeria-contaminated food or water is the main etiology. If Listeria travels outside the intestines, it can cause invasive listeriosis, such as sepsis, meningitis, and meningoencephalitis. Invasive illness is especially dangerous for pregnant women and their newborns, elderly people, and people with compromised immune systems or medical conditions such as end-stage kidney disease (ESKD) patients receiving long-term dialysis. Purpose: Describe the manifestations and hospital outcomes of invasive listeriosis and identify the risk factors for in-hospital and one-year mortality in ESKD patients receiving long-term dialysis. Patients and Methods: This retrospective observational study examined hospitalized patient records at a Taiwanese tertiary medical center from August 1, 2000, to August 31, 2021. ESKD patients on chronic dialysis were identified with invasive listeriosis by blood culture and discharge diagnosis. Over 21 years, we accurately recorded 26 cases. Results: ESKD patients on chronic dialysis with invasive listeriosis have a poor prognosis. Only 53.8% of chronic dialysis patients with invasive listeriosis survived their first hospital episode. 42.3% of hospitalized ESKD patients with invasive listeriosis survived one year later. In univariate analysis, shock, tachypnea (RR ≥ 22), respiratory failure, qSOFA score ≥ 2, and lower initial platelet count were linked to greater in-hospital mortality rates. Conclusion: ESKD patients with invasive listeriosis have a grave prognosis. Our research reveals that an early blood sample for a bacterial culture may identify invasive listeriosis in chronic dialysis patients with fever, nausea or vomiting, confusion, and respiratory distress. This study is the first to identify a lower platelet count and qSOFA score ≥ 2 as markers of high-risk invasive listeriosis in ESKD patients.

Epidemiology and outcomes of anal abscess in patients on chronic dialysis: a 14-year retrospective study

OBJECTIVES: We conducted this retrospective study to elucidate the clinical presentation and outcomes of anal abscess in chronic dialysis patients. METHODS: We performed a chart review of patients who were hospitalized for anal abscess from Jan. 2002 to Dec. 2015. A total of 3,074 episodes of anal abscess were identified. Of these, 43 chronic dialysis patients with first-time anal abscess were enrolled. Patients were divided into a surgical group and a nonsurgical group according to the treatment received during hospitalization. The baseline characteristics, clinical findings, treatments and outcomes were obtained and analyzed. The endpoints of this study were in-hospital mortality, one-year mortality and one-year recurrence. RESULTS: Of the 43 patients, 27 (62.7%) received surgical treatment, and 16 (37.2%) received antibiotic treatment alone. There was no significant difference in age, sex, body mass index, smoking habits, comorbidities, or dialysis characteristics between the two groups. Perianal abscess was the most common type of anal abscess, and 39.5% of patients experienced fistula formation. Most patients had mixed aerobic and anaerobic flora. Our data demonstrate that there was no significant difference in hospital stay, one-year survival or recurrence rate between the surgical group and nonsurgical group. However, there was a trend toward better in-hospital survival in patients who received surgical treatment (p=0.082). CONCLUSION: In chronic dialysis patients with anal abscess, there was no statistically significant difference in clinical presentation and outcomes between the surgical and nonsurgical groups, although the surgical group had a trend of better in-hospital survival.