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Deciphering dissolved organic matter (DOM) molecular complexity is crucial for understanding ecosystem function. Using the continental-scale Worldwide Hydrobiogeochemistry Observation Network for Dynamic Rivers Systems (WHONDRS) Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) dataset, we reveal fundamental scaling patterns of DOM chemodiversity with watershed characteristics. Analysis of 54 river sites shows local and regional watershed features significantly influence DOM chemodiversity (2500–8718 unique formulae), exhibiting consistent scaling patterns across compound classes and a novel latitudinal gradient (decreasing diversity with increasing latitude). Scaling relationships for DOM composition vary by compound class. Crucially, the scaling parameters (B, baseline chemodiversity; Z, sensitivity) are linearly interrelated. This B–Z relationship is most robust for potentially bio-labile carbohydrates (coefficient of determination R 2 ≈ 0.85), diminishing for recalcitrant, plant-derived molecules (such as lignin), and indicates (potential) biolability-dependent coupling between baseline diversity and environmental responsiveness. These quantitative scaling relationships, with scaling exponents ranging from − 2.1 to 2.2 across compound classes, enable prediction of DOM composition across watersheds, offering a framework to understand ecosystem responses to environmental change. This research bridges biogeochemistry and ecology, providing tools to anticipate molecular transformations across scales.

Understanding the relationship between the composition of the human gut microbiota and the ecological forces shaping it is of great importance; however, knowledge of the biogeographical and ecological relationships between physically interacting taxa is limited. Interbacterial antagonism may play an important role in gut community dynamics, yet the conditions under which antagonistic behaviour is favoured or disfavoured by selection in the gut are not well understood. Here, using genomics, we show that a species-specific type VI secretion system (T6SS) repeatedly acquires inactivating mutations in Bacteroides fragilis in the human gut. This result implies a fitness cost to the T6SS, but we could not identify laboratory conditions under which such a cost manifests. Strikingly, experiments in mice illustrate that the T6SS can be favoured or disfavoured in the gut depending on the strains and species in the surrounding community and their susceptibility to T6SS antagonism. We use ecological modelling to explore the conditions that could underlie these results and find that community spatial structure modulates interaction patterns among bacteria, thereby modulating the costs and benefits of T6SS activity. Our findings point towards new integrative models for interrogating the evolutionary dynamics of type VI secretion and other modes of antagonistic interaction in microbiomes. A combination of phylogenomics, mouse gut experimental assays and ecological modelling shows how community structure controls the fitness costs and benefits of the type VI secretion system in the human gut symbiont Bacteroides fragilis .

The medicinal leech is a developing experimental model of gut symbioses. Aeromonas veronii and Mucinivorans hirudinis are core members of the gut microbial community in Hirudo verbana and may aid the leech in digesting the blood meal, preserving the blood meal, and keeping invading bacteria from colonizing the gut. The bladders of H. verbana contain an entirely different microbial consortium. The scientific interest in this symbiosis is currently due to its simple nature and the extreme dietary habits of the leech. In order to increase the usefulness of this model, a more sophisticated understanding of processes by which the microbiome is acquired and develops is necessary. In my dissertation I have compared the gut and bladder microbiomes of H. verbana to that of Macrobdella decora (the North American medicinal leech) in order to determine the conservation of symbionts. I have additionally examined the potential for horizontal and vertical transmission of gut and bladder symbionts to hatchling and juvenile H. verbana. With such information, future researchers will be able to draw parallels between processes occurring in the leech to those occurring in other organisms. A more detailed understanding of processes conserved or lost between symbiotic partners will lead to a better understanding of processes required for colonization and persistence across a wide range of animals.

Splenic B-cells isolated from mice injected with LPS, differentiate into antibody-producing plasma cells in vitro. Pretreatment with TCDD, a potent immunosuppressive agent, impairs B-cell differentiation. Altered DNA methylation, an epigenetic event, may play a key role in this impairment. DNA was isolated from splenocytes prepared 6 days post experiment initiation from 5–6wk old female C57BL/6 mice dosed with: TCDD, 3 or 30μg/kg, on day 0; or LPS, 25μg/mouse, on day 4; or sequentially with TCDD and then LPS on days 0 and 4, respectively. To discern regions of altered DNA methylation (RAMs), DNA was restricted with HpaII (a methylation sensitive enzyme), followed by arbitrarily primed PCR and capillary electrophoresis. The mRNA expression of selected genes (annotated RAMs or genes closely affected by them) that might affect B-cell differentiation were analyzed using qRT-PCR. LPS, 3, or 30μg/kg TCDD alone resulted in 40, 43 and 42 RAMs, respectively, while LPS challenge subsequent to 3 or 30μg/kg TCDD resulted in 34 and 39 RAMs, respectively. Interestingly, the combined treatments lead to many RAMs observed in single treatments but also many unique RAMs. Three patterns of mRNA expression were observed: no change, similar changes in all groups, and different changes based upon treatment. Collectively, this research suggests a novel epigenetic mechanism potentially regulating gene expression stimulated by LPS and TCDD exposure and important in the differentiation of B-cells in the splenocyte population.

Understanding the relationship between the composition of the human gut microbiota and the ecological forces shaping it is of high importance as progress towards therapeutic modulation of the microbiota advances. However, given the inaccessibility of the gastrointestinal tract, our knowledge of the biogeographical and ecological relationships between physically interacting taxa has been limited to date. It has been suggested that interbacterial antagonism plays an important role in gut community dynamics, but in practice the conditions under which antagonistic behavior is favored or disfavored by selection in the gut environment are not well known. Here, using phylogenomics of bacterial isolate genomes and analysis of infant and adult fecal metagenomes, we show that the contact-dependent type VI secretion system (T6SS) is repeatedly lost from the genomes of in adults compare to infants. Although this result implies a significant fitness cost to the T6SS, but we could not identify conditions under which such a cost manifests. Strikingly, however, experiments in mice illustrated that the T6SS can be favored or disfavored in the gut environment, depending on the strains and species in the surrounding community and their susceptibility to T6SS antagonism. We use a variety of ecological modeling techniques to explore the possible local community structuring conditions that could underlie the results of our larger scale phylogenomic and mouse gut experimental approaches. The models illustrate robustly that the pattern of local community structuring in space can modulate the extent of interactions between T6SS-producing, sensitive, and resistant bacteria, which in turn control the balance of fitness costs and benefits of performing contact-dependent antagonistic behavior. Taken together, our genomic analyses, studies, and ecological theory point toward new integrative models for interrogating the evolutionary dynamics of type VI secretion and other predominant modes of antagonistic interaction in diverse microbiomes.

Diseases caused by the fish pathogens Flavobacterium columnare and Flavobacterium psychrophilum are major contributors of preventable losses in the aquaculture industry. The persistent and difficult to control infections caused by these bacteria make timely intervention and prophylactic elimination of pathogen reservoirs important measures to combat these disease-causing agents. In the present study, we present two independent assays for detecting these pathogens in a range of environmental samples. Natural water samples were inoculated with F. columnare and F. psychrophilum cells, and pathogen levels were detected using Illumina MiSeq sequencing and droplet digital PCR. Both detection methods accurately identified pathogen-positive samples and showed good agreement in quantifying each pathogen. Additionally, the real-world application of these approaches was demonstrated using environmental samples collected at a rainbow trout aquaculture facility. These results show that both methods can serve as useful tools for surveillance efforts in aquaculture facilities, where the early detection of these flavobacterial pathogens may direct preventative measures to reduce disease occurrence. Early detection of a deadly disease outbreak in a population can be the difference between mass fatality or mitigated effects. In the present study, we evaluated and compared two techniques for detecting economically impactful aquaculture pathogens. We demonstrate that one of these techniques, 16S rRNA gene sequencing using Illumina MiSeq technology, provides the ability to accurately detect two fish pathogens, F. columnare and F. psychrophilum, while simultaneously profiling the native microbial community. The second technique, droplet digital PCR, is commonly used for pathogen detection, and the results obtained using the assays we designed with this method served to validate those obtained using the MiSeq method. These two methods offer distinct advantages. The MiSeq method pairs pathogen detection and microbial community profiling to answer immediate and long-term fish health concerns, while droplet digital PCR method provides fast and highly sensitive detection that is useful for surveillance and rapid clinical responses.

Leeches are found in terrestrial, aquatic, and marine habitats on all continents. Sanguivorous leeches have been used in medicine for millennia. Modern scientific uses include studies of neurons, anticoagulants, and gut microbial symbioses. Hirudo verbana, the European medicinal leech, maintains a gut community dominated by two bacterial symbionts, Aeromonas veronii and Mucinivorans hirudinis, which sometimes account for as much as 97% of the total crop microbiota. The highly simplified gut anatomy and microbiome of H. verbana make it an excellent model organism for studying gut microbial dynamics. The North American medicinal leech, Macrobdella decora, is a hirudinid leech native to Canada and the northern U.S.A. In this study we show that M. decora symbiont communities are very similar to those in H. verbana. This similarity allowed for an extensive study in which wild caught animals were sampled to determine effects of geographic separation, time of collection, and feeding on the microbiome. Through 16S V4 rRNA deep sequencing we show that: i) the M. decora gut and bladder microbial communities are distinct, ii) the M. decora gut community is affected by feeding and long periods of starvation, and iii) geographic separation does not appear to affect the overall gut microbial community structure. We propose that M. decora is a replacement for H. verbana for studies of wild-caught animals and offer evidence for the conservation of annelid symbionts. Successful culturing and comparison of dominant symbionts from M. decora and H. verbana will provide the ability to assess host-symbiont co-evolution in future work.

As of October 21, 2022, a total of 27,884 monkeypox cases (confirmed and probable) have been reported in the United States. Gay, bisexual, and other men who have sex with men have constituted a majority of cases, and persons with HIV infection and those from racial and ethnic minority groups have been disproportionately affected (1,2). During previous monkeypox outbreaks, severe manifestations of disease and poor outcomes have been reported among persons with HIV infection, particularly those with AIDS (3-5). This report summarizes findings from CDC clinical consultations provided for 57 patients aged ≥18 years who were hospitalized with severe manifestations of monkeypox during August 10-October 10, 2022, and highlights three clinically representative cases. Overall, 47 (82%) patients had HIV infection, four (9%) of whom were receiving antiretroviral therapy (ART) before monkeypox diagnosis. Most patients were male (95%) and 68% were non-Hispanic Black (Black). Overall, 17 (30%) patients received intensive care unit (ICU)-level care, and 12 (21%) have died. As of this report, monkeypox was a cause of death or contributing factor in five of these deaths; six deaths remain under investigation to determine whether monkeypox was a causal or contributing factor; and in one death, monkeypox was not a cause or contributing factor.** Health care providers and public health professionals should be aware that severe morbidity and mortality associated with monkeypox have been observed during the current outbreak in the United States (6,7), particularly among highly immunocompromised persons. Providers should test all sexually active patients with suspected monkeypox for HIV at the time of monkeypox testing unless a patient is already known to have HIV infection. Providers should consider early commencement and extended duration of monkeypox-directed therapy in highly immunocompromised patients with suspected or laboratory-diagnosed monkeypox. Engaging all persons with HIV in sustained care remains a critical public health priority.

To the Editor: Blaum and Omura (June 11 issue) 1 report that they treated a case of cutaneous larva migrans with topical liquid-nitrogen cryotherapy. Apart from cryotherapy, various other therapeutic approaches have been used for this condition, including topical administration of thiabendazole and systemic administration of albendazole, thiabendazole, and ivermectin. 2 – 5 Since freezing is often ineffective and not devoid of side effects, 3 , 4 we conducted a prospective study of ivermectin, administered as a single oral dose of 12 mg, to travelers who had returned from various tropical or subtropical destinations. From 1993 to 1997, we treated 67 consecutive outpatients who had . . .

Esteemed critic Blanche Gelfant's brilliant companion gathers together lucid essays on major writers and themes by some of the best literary critics in the United States. Part 1 is comprised of articles on stories that share a particular theme, such as “Working Class Stories” or “Gay and Lesbian Stories.” The heart of the book, however, lies in Part 2, which contains more than one hundred pieces on individual writers and their work, including Fitzgerald, Hemingway, Richard Ford, Raymond Carver, Eudora Welty, Andre Debus, Zora Neal Hurston, Anne Beattie, Bharati Mukherjee, J. D. Salinger, and Jamaica Kincaid, as well as engaging pieces on the promising new writers to come on the scene.