Biology subjects

Campbell, B. J.

Publications and source records attributed to Campbell, B. J..

11 recordsLinked to original sources

bioRxiv2026

Plant Functional Type Composition, Rather Than Species Diversity, Shapes Soil Microbial Functional Diversity and Redundancy

Cover crops (CCs) are widely used to improve soil health, but their species-specific effects on microbial functional diversity and redundancy remain poorly understood. We evaluated how monocultures of field pea (Pisum sativum), forage radish (Raphanus sativus), and cereal rye (Secale cereale), as well as a three-species mixture (3spp) and a five-species mixture (5spp), influence rhizosphere bacterial and fungal communities in a field experiment. Amplicon sequencing and predictive functional profiling were used to assess microbial diversity, composition, functional potential, and functional redundancy (FR). Microbial alpha diversity showed little change across treatments, but community composition and predicted functional profiles were strongly influenced by CC identity. The 3spp rhizobiome showed the highest bacterial FR, broad metabolic capacity, and greater network connectivity, suggesting increased functional stability of all treatments. In contrast, the 5spp rhizobiome showed reduced bacterial FR and more widespread functional depletion, likely due to imbalances in plant functional types. Monocultures showed species-specific patterns, with rye supporting functionally efficient communities and radish promoting more competitive interactions and reduced functional diversity. Fungal communities responded differently from bacterial communities. While fungal taxonomic shifts were limited, they showed stronger compositional differences among treatments and more stable functional profiles. Notably, fungal FR was highest in the 5spp rhizobiome. Overall, these findings highlight that balanced plant functional composition, rather than greater species richness alone, is important for shaping rhizosphere microbial function and redundancy. Balanced mixtures promoted higher bacterial redundancy, while more diverse but functionally imbalanced mixtures did not consistently enhance microbial function. ImportanceThe benefits of using CCs in agricultural settings are mostly influenced by microbial communities, including nutrient cycling, organic matter turnover, and resilience to disturbance. However, CC mixtures are often promoted on the assumption that more species provide greater soil benefits. This work challenges that assumption by showing that the functional identity and balance of CC species may matter more than the number of species alone. This distinction is important for farmers, land managers, and researchers because CC seed mixes can be costly, and poorly balanced mixtures may fail to deliver intended microbial benefits. Understanding which plant combinations support functionally stable microbial communities can improve CC recommendations and help design agricultural systems that maintain soil processes under changing environmental conditions.

microbiology↗

bioRxiv2026

Environmental Gradients Shape the Hydrocarbon-Degrading Microbiome in Two Mid Atlantic Bays.

Hydrocarbons are recalcitrant organic matter that are released into the environment via natural and anthropogenic activities. We hypothesized that abiotic and biotic factors, including salinity, temperature, seasonality, microbial interactions, and functional redundancy, influence the abundance and activity of potential hydrocarbon degraders in the Delaware and Chesapeake Bays. We identified key genes in hydrocarbon degradation pathways in metagenomes, metatranscriptomes, and metagenome assembled genomes (MAGs) from these estuaries. Aerobic aromatic and alkane degradation pathways predominated in both estuaries, with higher gene abundances observed in low-salinity spring and summer samples. Hydrocarbon degrading MAG abundance were significantly structured by salinity, temperature, nitrate, and silicate concentrations. Metatranscriptomic analyses revealed consistently higher expression of aerobic alkane and aromatic degradation genes in the Delaware compared to the Chesapeake Bay, with the highest occurring under low-salinity spring conditions in the former. Catechol degradation pathways exhibited high functional redundancy, whereas the naphthalene degradation pathway showed restricted distribution. Co-expression analysis revealed that Burkholderiales displayed condition dependent metabolic coupling while Pseudomonadales integrated hydrocarbon degradation with fermentation and central metabolism, demonstrating complementary strategies that support multi-scale ecosystem resilience. In conclusion, environmental gradients and taxon-specific metabolic strategies together govern hydrocarbon degradation potential in these estuaries, with implications for predicting ecosystem responses to hydrocarbon inputs under changing conditions. ImportanceCoastal estuaries are among the most contaminated aquatic environments on Earth, receiving continuous hydrocarbon inputs from industrial activity, urban runoff, and natural sources. Microorganisms are the primary agents of hydrocarbon breakdown in these systems yet predicting when and where this capacity is active and how resilient it is to environmental change remains a major challenge. Using paired genomic and transcriptomic data from microbial genomes across two major mid-Atlantic estuaries, we show that hydrocarbon degradation capacity is not uniformly distributed but is instead shaped by salinity, nutrients, and seasonality in pathway-specific ways. Critically, dominant degrader taxa employ fundamentally different metabolic strategies to sustain this function across fluctuating conditions, providing a form of community-level insurance against environmental disturbance. These findings advance our ability to predict microbial hydrocarbon degradation in coastal systems and inform nature-based approaches to bioremediation under increasing climate and anthropogenic pressures.

genomics↗

bioRxiv2025

Ecological distribution, environmental roles and drivers of Actinobacteriota in two Mid-Atlantic estuaries

Actinobacteriota, a bacterial phylum renowned for members that produce bioactive compounds (e.g., antibiotics), has key roles in terrestrial and aquatic ecosystems. Although soil and marine/freshwater Actinobacteriota are well studied, functions and activities of their estuarine counterparts are poorly understood. We characterized 67 metagenome-assembled genomes (MAGs) belonging to 12 Actinobacteriota families from Chesapeake and Delaware Bay water samples across different seasons, salinities, and size fractions. MAGs from four dominant families, Ilumatobacteraceae, Nanopelagicaceae, Microbacteriaceae, and S36-B12, were examined in depth for their abundance, functional potential, estimated growth rates, and gene expression among samples. Actinobacteriota were most abundant in low- to medium-salinity samples during spring and summer. Their abundance patterns were strongly influenced by combinations of salinity, temperature, and phosphate, nitrate and silicate concentrations. Notably, many exhibited high estimated growth rates under low and medium salinities in summer. Members of the four major families showed a range of metabolic capacities from generalist to specialist, and all encoded biosynthetic gene clusters (BGCs) for secondary metabolites, particularly terpenes and betalactones, that were differentially expressed across conditions. Bay, salinity and size fraction were the primary drivers of gene expression differences. Distinct secondary metabolite genes were expressed between bays, with higher expression generally observed in medium compared to low salinities. These findings underscore the metabolic versatility and environmental responsiveness of Actinobacteriota, highlighting their active role in estuarine microbial communities and their contributions to biogeochemical cycling in dynamic coastal ecosystems. ImportanceEstuaries are dynamic transition zones where microbial communities play key roles in nutrient cycling and ecosystem functioning. This study provides new insights into the distribution of Actinobacteriota families and their responses to salinity and nutrient gradients in two major U.S. estuaries, the Chesapeake and Delaware Bays. We characterized the potential roles of Actinobacteriota in biogeochemical processes and secondary metabolite production, which may influence broad microbial interactions. These bacteria may also serve as a source of novel bioactive compounds, including antibiotics. By integrating omic and environmental data, this work advances our understanding of Actinobacteriota adaptations and their ecology in estuarine environments.

microbiology↗

bioRxiv2023

Optimisation of a DNA extraction protocol for improving the bacterial and fungal classification based on Nanopore sequencing

Ribosomal RNA gene amplicon sequencing is commonly used to evaluate microbiome profiles in health and disease and document the impact of interventional treatments. Long-read nanopore sequencing is attractive since it can provide greater classification at the species level. However, optimised protocols to target marker genes for bacterial and fungal profiling are needed. To achieve an increased taxonomic resolution, we developed extraction and long-amplicon PCR-based approaches using Nanopore sequencing. Three sample lysis conditions were applied to a mock microbial community, including known bacterial and fungal species; the 96 MagBead DNA lysis buffer (ML) alone, incorporating bead-beating (MLB) or bead-beating plus MetaPolyzyme enzymatic treatment (MLBE). Profiling of bacterial comparison, MLB had more statistically different bacterial phyla and genera than the others. For fungal profiling, MLB had a significant increase of Ascomycota and a decline of Basidiomycota, subsequently failing to detect Malassezia and Cryptococcus. Also, the principal coordinates analysis (PCoA) plot by the Bray-Curtis index showed a significant difference among groups for bacterial (p = 0.033) and fungal (p = 0.012) profiles. Overall, the microbial profiling and diversity analysis revealed that ML and MLBE have more similarity than MLB for both bacteria and fungi, therefore, bead-beating is not recommended for long-read amplicon sequencing. However, ML alone was suggested as an optimal approach considering DNA yield, classification, reagent cost and hands-on time. This could be an initial proof-of-concept study for simultaneous human microbiome and mycobiome studies.

microbiology↗

bioRxiv2022

Controls of SAR11 subclade abundance, diversity, and growth in two Mid-Atlantic estuaries

SAR11 is a dominant bacterial clade in marine oligotrophic ecosystems. SAR11 can also be dominant in estuarine systems, where they are not well-studied. We examined the effects of season, nutrient concentrations, and salinity in shaping SAR11 subclade abundance, diversity, function, and growth in two Mid-Atlantic estuaries, the Delaware and Chesapeake Bays. Using metagenome-assembled genomes, we identified twelve distinct genomospecies within the Ia, II, IIIa, and V subclades, which made up to 60% of the total bacterial community. The functional potential of all SAR11 genomospecies varied, especially in carbohydrate metabolism, transporters, and one-carbon metabolic pathways. Predicted growth rates, estimated by the Peak to Trough method, varied by season and genomospecies. SAR11 growth rates negatively correlated in the spring but positively correlated in the summer with chlorophyll a concentrations and bacterial production, as well as phosphate and ammonium concentrations. Genomospecies in Ia.1, IIIa.2, and IIIa.4 subclades had low growth rates, while genomospecies in Ia.3, Ia.5, Ia.6, II, and V subclades had higher and more variable growth rates that were positively correlated with phosphate concentrations and temperature. Growth rate variation between subclades was associated with carbohydrate metabolic gene repertoires, especially glycolysis and number of transporters. While total transcript to genome ratios generally mirrored growth rates, transcription of genes involved in phosphate and nitrogen transport were negatively associated with growth rates. These data suggest that SAR11 genomospecies abundance varies in these estuaries because of differences in growth rates and metabolic capacities in response to changes in environmental conditions. ImportanceThe SAR11 clade is one of the most abundant bacterial groups in marine systems, including many estuaries. From the Delaware Bay and Chesapeake Bay environmental metagenomes, we reconstructed nearly complete SAR11 metagenome-assembled genomes representing ten genomospecies in four subclades, of which at least one is novel. Growth rate estimates of genomospecies correlated with functional gene repertoires of carbohydrate transporter and metabolism. Different SAR11 genomospecies dominated among the seasons, depending on their growth rates, biological productivity, and nutrient concentrations. Our RNAseq approach facilitated an understanding of the environmental controls on the abundance of SAR11 genomospecies in their natural habitat. This study is the first to combine multiple measures of diversity, abundance, functional potential, growth rates and activity of this important group, demonstrating a direct link between SAR11 genomospecies abundance and growth in the context of its environment.

microbiology↗

bioRxiv2020

Ecology of inorganic sulfur auxiliary metabolism in widespread bacteriophages

Microbial sulfur metabolism contributes to biogeochemical cycling on global scales. Sulfur metabolizing microbes are infected by phages that can encode auxiliary metabolic genes (AMGs) to alter sulfur metabolism within host cells but remain poorly characterized. Here we identified 191 phages derived from twelve environments that encoded 227 AMGs for oxidation of sulfur and thiosulfate (dsrA, dsrC/tusE, soxC, soxD and soxYZ). Evidence for retention of AMGs during niche-differentiation of diverse phage populations provided evidence that auxiliary metabolism imparts measurable fitness benefits to phages with ramifications for ecosystem biogeochemistry. Gene abundance and expression profiles of AMGs suggested significant contributions by phages to sulfur and thiosulfate oxidation in freshwater lakes and oceans, and a sensitive response to changing sulfur concentrations in hydrothermal environments. Overall, our study provides novel insights on the distribution, diversity and ecology of phage auxiliary metabolism associated with sulfur and reinforces the necessity of incorporating viral contributions into biogeochemical configurations.

microbiology↗

bioRxiv2019

Rare microbes from diverse Earth biomes dominate community activity

Microbes are the Earths most numerous organisms and are instrumental in driving major global biological and chemical processes. Microbial activity is a crucial component of all ecosystems, as microbes have the potential to control any major biochemical process. In recent years, considerable strides have been made in describing the community structure, i.e. diversity and abundance, of microbes from the Earths major biomes. In virtually all environments studied, a few highly abundant taxa dominate the structure of microbial communities. Still, microbial diversity is high and is concentrated in the less abundant, or rare, fractions of the community, i.e. the \"long tail\" of the abundance distribution. The relationship between microbial community structure and activity, specifically the role of rare microbes, and its connection to ecosystem function, is not fully understood. We analyzed 12.3 million metagenomic and metatranscriptomic sequence assemblies and their genes from environmental, human, and engineered microbiomes, and show that microbial activity is dominated by rare microbes (96% of total activity) across all measured biomes. Further, rare microbial activity was comprised of traits that are fundamental to ecosystem and organismal health, e.g. biogeochemical cycling and infectious disease. The activity of rare microbes was also tightly coupled to temperature, revealing a link between basic biological processes, e.g. reaction rates, and community activity. Our study provides a broadly applicable and predictable paradigm that implicates rare microbes as the main microbial drivers of ecosystem function and organismal health.

microbiology↗

bioRxiv2019

Long-term iron deficiency and iron supplementation exacerbate acute DSS-induced colitis and are associated with significant dysbiosis

Patients taking oral iron supplementation often suffer from gastrointestinal side effects. We have previously shown that acute alterations in oral iron exacerbate dextran sodium sulphate (DSS) induced colitis and are associated with dysbiosis. As patients take iron supplementation for long periods, we asked whether this too would influence colitis and the microbiome. We assessed the impact of long-term changes in dietary iron, by feeding chow containing 100ppm, 200ppm and 400ppm (reflecting a deficient, normal or supplemented diet, respectively) for up to 9 weeks to female wild-type C57BL/6 (WT) mice in presence or absence of chronic colitis, or acute colitis induced after 8 weeks, induced by DSS. Assessment was made based on (i) clinical and histological severity of colitis, and (ii) faecal microbial diversity, as assessed by sequencing the V4 region of 16S rRNA. In mice with long term changes to their dietary iron, reduced iron intake (100ppm iron diet) was associated with increased weight loss and histology scoring in the acute colitis model. Chronic colitis was not influenced by altering dietary iron however there was a clear change in the faecal microbiome in the 100 and 400ppm iron DSS-treated groups and in controls consuming the 400ppm iron diet. Proteobacteria levels increased significantly at day-63 compared to baseline and Bacteroidetes levels decreased in the 400ppm iron DSS group at day-63 compared to baseline; mirroring our previously published work in acute colitis. Long term dietary iron alterations clearly affects gut microbiota signatures but do not appear to exacerbate chronic colitis. However, acute colitis is exacerbated by changes in dietary iron. More work is needed to understand the impact of iron supplementation of the pathologenesis of IBD and rise that possiblity that the change in the microbiome, in patients with colitis, is a consequence of the increase in luminal iron and not simply the presence of colitis.

pathology↗

bioRxiv2019

Macrophage-specific NF-kappa B activation dynamics can segregate inflammatory bowel disease patients

The heterogeneous nature of inflammatory bowel disease (IBD) presents challenges, particularly when choosing therapy. Activation of the NF-{kappa}B transcription factor is a highly-regulated, dynamic event in IBD pathogenesis. We expressed the human NF-{kappa}B/p65 subunit in blood-derived macrophages, using lentivirus. Confocal imaging of p65 activation revealed that a higher proportion of macrophages from Crohns patients responded to lipid-A compared to controls. In contrast, cells from ulcerative colitis (UC) patients exhibited a shorter duration of p65 nuclear localisation compared to healthy controls and Crohns donors. Using a similar lentivirus approach, NF-{kappa}B-regulated luciferase was expressed in patient macrophages, isolated from frozen peripheral blood mononuclear cell samples. Following activation, samples could be segregated into three clusters based on the NF-{kappa}B-regulated luciferase response. The majority of UC samples appeared in hypo-responsive cluster 1, with Crohns patients representing the majority of hyper-responsive cluster 3. A positive correlation was seen between NF-{kappa}B-induced luciferase activity and cytokine levels released to medium from stimulated macrophages, but not in serum or biopsy. Analysis of macrophage cytokine responses and patient metadata revealed a strong correlation between Crohns patients who smoked and hyper-activation of p65. These in vitro dynamic assays of NF-{kappa}B activation in blood-derived macrophages segregate IBD patients into groups with different phenotypes and therefore may help determine response to therapy. Significance statementThis manuscript describes two dynamic assays of NF-{kappa}B activation in blood-derived macrophages that can segregate IBD patients into groups with different phenotypes. For the first time we introduce the use of dynamic measurements of a transcription factor activation as a method to stratify patients and we are confident that our approach will lead in future to early patient stratification and prediction of treatment outcome.

immunology↗

bioRxiv2019

Identification of a novel therapeutic agent for Inflammatory Bowel Disease guided by systems medicine

ObjectiveInflammatory bowel diseases cause significant morbidity and mortality. Aberrant NF-{kappa}B signalling is strongly associated with these conditions, and several established drugs influence the NF-{kappa}B signalling network to exert their effect. This study aimed to identify drugs which alter NF-{kappa}B signalling and may be repositioned for use in inflammatory bowel disease. DesignThe SysmedIBD consortium established a novel drug-repurposing pipeline based on a combination of in-silico drug discovery and biological assays targeted at demonstrating an impact on NF-kappaB signalling, and a murine model of IBD. ResultsThe drug discovery algorithm identified several drugs already established in IBD, including corticosteroids. The highest-ranked drug was the macrolide antibiotic Clarithromycin, which has previously been reported to have anti-inflammatory effects in aseptic conditions. Clarithromycins effects were validated in several experiments: it influenced NF-{kappa}B mediated transcription in murine peritoneal macrophages and intestinal enteroids; it suppressed NF-{kappa}B protein shuttling in murine reporter enteroids; it suppressed NF-{kappa}B (p65) DNA binding in the small intestine of mice exposed to LPS, and it reduced the severity of dextran sulphate sodium-induced colitis in C57BL/6 mice. Clarithromycin also suppressed NF-{kappa}B (p65) nuclear translocation in human intestinal enteroids. ConclusionsThese findings demonstrate that in-silico drug repositioning algorithms can viably be allied to laboratory validation assays in the context of inflammatory bowel disease; and that further clinical assessment of clarithromycin in the management of inflammatory bowel disease is required.

systems biology↗

bioRxiv2018

Oral iron exacerbates colitis and influences the intestinal microbiome

Inflammatory bowel disease (IBD) is associated with anaemia and oral iron replacement to correct this can be problematic, intensifying inflammation and tissue damage. The intestinal microbiota also plays a key role in the pathogenesis of IBD, and iron supplementation likely influences gut bacterial diversity in patients with IBD. Here, we assessed the impact of dietary iron, using chow diets containing either 100, 200 or 400 ppm, fed ad libitum to adult female C57BL/6 mice in the presence or absence of colitis induced using dextran sulfate sodium (DSS), on (i) clinical and histological severity of acute DSS-induced colitis, and (ii) faecal microbial diversity, as assessed by sequencing the V4 region of 16S rRNA. Increasing or decreasing dietary iron concentration from the standard 200 ppm exacerbated both clinical and histological severity of DSS-induced colitis. DSS-treated mice provided only half the standard levels of iron ad libitum (i.e. chow containing 100 ppm iron) lost more body weight than those receiving double the amount of standard iron (i.e. 400 ppm); p<0.01. Faecal calprotectin levels were significantly increased in the presence of colitis in those consuming 100 ppm iron at day 8 (5.94-fold) versus day-10 group (4.14-fold) (p<0.05), and for the 400 ppm day-8 group (8.17-fold) versus day-10 group (4.44-fold) (p<0.001). In the presence of colitis, dietary iron at 400 ppm resulted in a significant reduction in faecal abundance of Firmicutes and Bacteroidetes, and increase of Proteobacteria, changes which were not observed with lower dietary intake of iron at 100 ppm. Overall, altering dietary iron intake exacerbated DSS-induced colitis; increasing the iron content of the diet also led to changes in intestinal bacteria diversity and composition after colitis was induced with DSS.

physiology↗