Charles R. Lovell

Bio: Charles R. Lovell is an academic researcher from University of South Carolina. The author has contributed to research in topics: Diazotroph & Spartina alterniflora. The author has an hindex of 37, co-authored 78 publications receiving 4130 citations.

Microbial Surface Colonization and Biofilm Development in Marine Environments

Abstract: SUMMARY Biotic and abiotic surfaces in marine waters are rapidly colonized by microorganisms. Surface colonization and subsequent biofilm formation and development provide numerous advantages to these organisms and support critical ecological and biogeochemical functions in the changing marine environment. Microbial surface association also contributes to deleterious effects such as biofouling, biocorrosion, and the persistence and transmission of harmful or pathogenic microorganisms and their genetic determinants. The processes and mechanisms of colonization as well as key players among the surface-associated microbiota have been studied for several decades. Accumulating evidence indicates that specific cell-surface, cell-cell, and interpopulation interactions shape the composition, structure, spatiotemporal dynamics, and functions of surface-associated microbial communities. Several key microbial processes and mechanisms, including (i) surface, population, and community sensing and signaling, (ii) intraspecies and interspecies communication and interaction, and (iii) the regulatory balance between cooperation and competition, have been identified as critical for the microbial surface association lifestyle. In this review, recent progress in the study of marine microbial surface colonization and biofilm development is synthesized and discussed. Major gaps in our knowledge remain. We pose questions for targeted investigation of surface-specific community-level microbial features, answers to which would advance our understanding of surface-associated microbial community ecology and the biogeochemical functions of these communities at levels from molecular mechanistic details through systems biological integration.

Bacterial Primary Colonization and Early Succession on Surfaces in Marine Waters as Determined by Amplified rRNA Gene Restriction Analysis and Sequence Analysis of 16S rRNA Genes

Abstract: The nearly universal colonization of surfaces in marine waters by bacteria and the formation of biofilms and biofouling communities have important implications for ecological function and industrial processes. However, the dynamics of surface attachment and colonization in situ, particularly during the early stages of biofilm establishment, are not well understood. Experimental surfaces that differed in their degrees of hydrophilicity or hydrophobicity were incubated in a salt marsh estuary tidal creek for 24 or 72 h. The organisms colonizing these surfaces were examined by using a cultivation-independent approach, amplified ribosomal DNA restriction analysis. The goals of this study were to assess the diversity of bacterial colonists involved in early succession on a variety of surfaces and to determine the phylogenetic affiliations of the most common early colonists. Substantial differences in the representation of different cloned ribosomal DNA sequences were found when the 24- and 72-h incubations were compared, indicating that some new organisms were recruited and some other organisms were lost. Phylogenetic analyses of the most common sequences recovered showed that the colonists were related to organisms known to inhabit surfaces or particles in marine systems. A total of 22 of the 26 clones sequenced were affiliated with the Roseobacter subgroup of the α subdivision of the division Proteobacteria (α-Proteobacteria), and most of these clones were recovered at a high frequency from all surfaces after 24 or 72 h of incubation. Two clones were affiliated with the Alteromonas group of the γ-Proteobacteria and appeared to be involved only in the very early stages of colonization (within the first 24 h). A comparison of the colonization patterns on the test surfaces indicated that the early bacterial community succession rate and/or direction may be influenced by surface physicochemical properties. However, organisms belonging to the Roseobacter subgroup are ubiquitous and rapid colonizers of surfaces in coastal environments.

Frontiers of Ecology

Abstract: integration and collaboration as we meet the challenge of understanding the great complexity of biological systems. Ecological subdisciplines are rapidly combining and incorporating other biological, physical, mathematical, and sociological disciplines. The burgeoning base of theoretical and empirical work, made possible by new methods, technologies, and funding opportunities, is providing the opportunity to reach robust answers to major ecological questions. In December 1999 the National Science Foundation convened a white paper committee to evaluate what we know and do not know about important ecological processes, what hurdles currently hamper our progress, and what intellectual and conceptual interfaces need to be encouraged. The committee distilled the discussion into four frontiers in research on the ecological structure of the earth’s biological diversity and the ways in which ecological processes continuously shape that structure (i.e., ecological dynamics). This article summarizes the discussions of those frontiers and explains why they are crucial to our understanding of how ecological processes shape patterns and dynamics of global biocomplexity. The frontiers are 1. Dynamics of coalescence in complex communities 2. Evolutionary and historical determinants of ecological processes: The role of ecological memory 3. Emergent properties of complex systems: Biophysical constraints and evolutionary attractors 4. Ecological topology: Defining the spatiotemporal domains of causality for ecological structure and processes Each of the four research frontiers takes a different approach to the overall ecological dynamics of biocomplexity, and all require integration and collaboration among those approaches. These overlapping frontiers themselves are not necessarily new. Within each frontier, however, are emerging questions and approaches that will help us understand how ecological processes are interconnected over multiple spatial and temporal scales, from local community structure to global patterns.

Molecular Analysis of Diazotroph Diversity in the Rhizosphere of the Smooth Cordgrass, Spartina alterniflora

Abstract: N(2) fixation by diazotrophic bacteria associated with the roots of the smooth cordgrass, Spartina alterniflora, is an important source of new nitrogen in many salt marsh ecosystems. However, the diversity and phylogenetic affiliations of these rhizosphere diazotrophs are unknown. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified nifH sequence segments was used in previous studies to examine the stability and dynamics of the Spartina rhizosphere diazotroph assemblages in the North Inlet salt marsh, near Georgetown, S.C. In this study, plugs were taken from gel bands from representative DGGE gels, the nifH amplimers were recovered and cloned, and their sequences were determined. A total of 59 sequences were recovered, and the amino acid sequences predicted from them were aligned with sequences from known and unknown diazotrophs in order to determine the types of organisms present in the Spartina rhizosphere. We recovered numerous sequences from diazotrophs in the gamma subdivision of the division Proteobacteria (gamma-Proteobacteria) and from various anaerobic diazotrophs. Diazotrophs in the alpha-Proteobacteria were poorly represented. None of the Spartina rhizosphere DGGE band sequences were identical to any known or previously recovered environmental nifH sequences. The Spartina rhizosphere diazotroph assemblage is very diverse and apparently consists mainly of unknown organisms.

High Frequency of Virulence Factor Genes tdh, trh, and tlh in Vibrio parahaemolyticus Strains Isolated from a Pristine Estuary

Abstract: Virulence factor genes encoding the thermostable direct hemolysin (tdh) and the thermostable direct hemolysin-related hemolysin (trh) are strongly correlated with virulence of the emergent human pathogen Vibrio parahaemolyticus. The gene encoding the thermolabile hemolysin (tlh) is also considered a signature molecular marker for the species. These genes are typically reported in very low percentages (1 to 2%) of nonclinical strains. V. parahaemolyticus strains were isolated from various niches within a pristine estuary (North Inlet, SC) and were screened for these genes using both newly designed PCR primers and more commonly used primers. DNA sequences of tdh and trh were recovered from 48% and 8.3%, respectively, of these North Inlet strains. The recovery of pathogenic V. parahaemolyticus strains in such high proportions from an estuarine ecosystem that is virtually free of anthropogenic influences indicates the potential for additional, perhaps environmental roles of the tdh and trh genes.

Effects of biodiversity on ecosystem functioning: a consensus of current knowledge

Abstract: Humans are altering the composition of biological communities through a variety of activities that increase rates of species invasions and species extinctions, at all scales, from local to global. These changes in components of the Earth's biodiversity cause concern for ethical and aesthetic reasons, but they also have a strong potential to alter ecosystem properties and the goods and services they provide to humanity. Ecological experiments, observations, and theoretical developments show that ecosystem properties depend greatly on biodiversity in terms of the functional characteristics of organisms present in the ecosystem and the distribution and abundance of those organisms over space and time. Species effects act in concert with the effects of climate, resource availability, and disturbance regimes in influencing ecosystem properties. Human activities can modify all of the above factors; here we focus on modification of these biotic controls. The scientific community has come to a broad consensus on many aspects of the re- lationship between biodiversity and ecosystem functioning, including many points relevant to management of ecosystems. Further progress will require integration of knowledge about biotic and abiotic controls on ecosystem properties, how ecological communities are struc- tured, and the forces driving species extinctions and invasions. To strengthen links to policy and management, we also need to integrate our ecological knowledge with understanding of the social and economic constraints of potential management practices. Understanding this complexity, while taking strong steps to minimize current losses of species, is necessary for responsible management of Earth's ecosystems and the diverse biota they contain.

Phylogenies and Community Ecology

Abstract: ▪ Abstract As better phylogenetic hypotheses become available for many groups of organisms, studies in community ecology can be informed by knowledge of the evolutionary relationships among coexisting species. We note three primary approaches to integrating phylogenetic information into studies of community organization: 1. examining the phylogenetic structure of community assemblages, 2. exploring the phylogenetic basis of community niche structure, and 3. adding a community context to studies of trait evolution and biogeography. We recognize a common pattern of phylogenetic conservatism in ecological character and highlight the challenges of using phylogenies of partial lineages. We also review phylogenetic approaches to three emergent properties of communities: species diversity, relative abundance distributions, and range sizes. Methodological advances in phylogenetic supertree construction, character reconstruction, null models for community assembly and character evolution, and metrics of community ...

Resistance, resilience, and redundancy in microbial communities

Abstract: Although it is generally accepted that plant community composition is key for predicting rates of ecosystem processes in the face of global change, microbial community composition is often ignored in ecosystem modeling. To address this issue, we review recent experiments and assess whether microbial community composition is resistant, resilient, or functionally redundant in response to four different disturbances. We find that the composition of most microbial groups is sensitive and not immediately resilient to disturbance, regardless of taxonomic breadth of the group or the type of disturbance. Other studies demonstrate that changes in composition are often associated with changes in ecosystem process rates. Thus, changes in microbial communities due to disturbance may directly affect ecosystem processes. Based on these relationships, we propose a simple framework to incorporate microbial community composition into ecosystem process models. We conclude that this effort would benefit from more empirical data on the links among microbial phylogeny, physiological traits, and disturbance responses. These relationships will determine how readily microbial community composition can be used to predict the responses of ecosystem processes to global change.

Bacterial production in fresh and saltwater ecosystems: a cross-system overview

Abstract: Heterotrophic bacteria are thought to be important components of aquatic ecosystems in several ways. These bacteria remineralize organic materials and convert some organic material into bacterial biomass. We examined data from 70 studies in which estimates of production of heterotrophic bacterial biomass (bacterial production) were reported for freshand saltwater ecosystems. In sediments, bacterial production was sigdicantly (p <0.001), positively correlated to sediment organic C content. Systems which had hlgh rates of benthic primary production (such as coral reefs) had rates of bacterial production greater than those predicted by sediment organic C content alone. In the photic zone of lakes and the ocean, bacterial production was significantly correlated with planktonic primary production, chlorophyll a, or numbers of planktonic bacteria. For all planktonic systems analysed, bacterial production ranged from 0.4 to 150 pg C 1-' d-' and averaged 20 % (median 16.5 %) of planktonic primary production. On an area1 basis for the entire water column, bacterial production ranged from 118 to 2439 mg m-2 d-' and averaged 30 % (median 27 %) of water column primary production. Heterotrophic bacterial production is, thus, a large component of total secondary production and is roughly twice as large as the production of macrozooplankton for a given level of primary production.

Antibiotics in early life alter the murine colonic microbiome and adiposity

Abstract: Antibiotics administered in low doses have been widely used as growth promoters in the agricultural industry since the 1950s, yet the mechanisms for this effect are unclear. Because antimicrobial agents of different classes and varying activity are effective across several vertebrate species, we proposed that such subtherapeutic administration alters the population structure of the gut microbiome as well as its metabolic capabilities. We generated a model of adiposity by giving subtherapeutic antibiotic therapy to young mice and evaluated changes in the composition and capabilities of the gut microbiome. Administration of subtherapeutic antibiotic therapy increased adiposity in young mice and increased hormone levels related to metabolism. We observed substantial taxonomic changes in the microbiome, changes in copies of key genes involved in the metabolism of carbohydrates to short-chain fatty acids, increases in colonic short-chain fatty acid levels, and alterations in the regulation of hepatic metabolism of lipids and cholesterol. In this model, we demonstrate the alteration of early-life murine metabolic homeostasis through antibiotic manipulation.