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PubMed2025

Concurrent stimulation of diflufenican biodegradation and changes in the active microbiome in gravel revealed by Total RNA.

The use of slowly degraded pesticides poses a particular problem when these are applied to urban areas such as gravel paths. The urban gravel provides an environment very different from agricultural soils; i.e., it is both lower in carbon and microbial activity. We, therefore, endeavored to stimulate the degradation of the pesticide diflufenican added to urban gravel microcosms amended with dry alfalfa to increase microbial activity. In the present study, alfalfa addition significantly increased the formation of diflufenican's primary metabolite, 2-[3-(trifluoromethyl)phenoxy]nicotinic acid (AE-B), indicating stimulated biotransformation. The concurrent changes of the active microbial communities within the gravel were explored using shotgun metatranscriptomic sequencing of ribosomal RNA and messenger RNA. Although bacterial taxa remained dominant (87.0%-98.5% relative abundance), the alfalfa treatment led to a 4-5-fold increase in eukaryotic groups, including fungi and microbial grazers. Several microbial taxa potentially involved in the degradation of complex carbon compounds and aromatic pollutants-including Bacteroidetes, Verrucomicrobia, Sordariomycetes, Mortierellales, Tremellales, Sphingopyxis, and Phenylobacterium-increased in relative abundance following alfalfa amendment. Functional gene profiling revealed elevated expression of genes related to microbial activity and biomass production. Genes with potential roles in the breakdown of complex carbon structures (e.g., xylanases/chitin deacetylases) and in the transformation of aromatic compounds (e.g., ring-cleaving dioxygenases) were revealed. We conclude that complex carbon amendments can enhance the microbial activity, promoting the biotransformation of diflufenican in urban gravel environments. These findings provide new insights into the interactions between microbial community dynamics, gene expression profiles, and pesticide biotransformation in non-agricultural matrices.IMPORTANCEPesticides used on urban areas, e.g., gravel paths, are likely to have different effects and fates than when these are used on agricultural soils. Hence, studies into the degradation of pesticides applied to urban matrices are needed. We have previously shown that metabolites of the persistent pesticide diflufenican are even more persistent in urban soils, and it has also previously been shown that these metabolites leach from gravel surfaces. The reasons behind this are that the urban gravel provides an environment very different from agricultural soils; i.e., it is both lower in carbon and microbial activity. In the present study, we, therefore, endeavored to stimulate the degradation of the pesticide diflufenican added to urban gravel microcosms amended with dry alfalfa to increase microbial activity, concurrently studying the changes in the active microbiome by Total RNA-metatranscriptomics.

Biodegradation, Environmental↗

PubMed2004

Metagenomics: genomic analysis of microbial communities.

Uncultured microorganisms comprise the majority of the planet's biological diversity. Microorganisms represent two of the three domains of life and contain vast diversity that is the product of an estimated 3.8 billion years of evolution. In many environments, as many as 99% of the microorganisms cannot be cultured by standard techniques, and the uncultured fraction includes diverse organisms that are only distantly related to the cultured ones. Therefore, culture-independent methods are essential to understand the genetic diversity, population structure, and ecological roles of the majority of microorganisms. Metagenomics, or the culture-independent genomic analysis of an assemblage of microorganisms, has potential to answer fundamental questions in microbial ecology. This review describes progress toward understanding the biology of uncultured Bacteria, Archaea, and viruses through metagenomic analyses.

Archaea↗

PubMed2005

Effects of fire on properties of forest soils: a review.

Many physical, chemical, mineralogical, and biological soil properties can be affected by forest fires. The effects are chiefly a result of burn severity, which consists of peak temperatures and duration of the fire. Climate, vegetation, and topography of the burnt area control the resilience of the soil system; some fire-induced changes can even be permanent. Low to moderate severity fires, such as most of those prescribed in forest management, promote renovation of the dominant vegetation through elimination of undesired species and transient increase of pH and available nutrients. No irreversible ecosystem change occurs, but the enhancement of hydrophobicity can render the soil less able to soak up water and more prone to erosion. Severe fires, such as wildfires, generally have several negative effects on soil. They cause significant removal of organic matter, deterioration of both structure and porosity, considerable loss of nutrients through volatilisation, ash entrapment in smoke columns, leaching and erosion, and marked alteration of both quantity and specific composition of microbial and soil-dwelling invertebrate communities. However, despite common perceptions, if plants succeed in promptly recolonising the burnt area, the pre-fire level of most properties can be recovered and even enhanced. This work is a review of the up-to-date literature dealing with changes imposed by fires on properties of forest soils. Ecological implications of these changes are described.

Animals↗

PubMed2003

Manadomanzamines A and B: a novel alkaloid ring system with potent activity against mycobacteria and HIV-1.

Two novel alkaloids, named manadomanzamines A (1) and B (2), were isolated from an Indonesian sponge Acanthostrongylophora sp. (Haplosclerida: Petrosiidae). Their structures were elucidated and shown to be a novel organic skeleton related to the manzamine type alkaloids. Their absolute configuration and conformation were determined by CD, NOESY, and molecular modeling analysis. The microbial community analysis for the sponge that produces these unprecedented alkaloids has also been completed. Manadomanzamines A (1) and B (2) exhibited strong activity against Mycobacterium tuberculosis (Mtb) with MIC values of 1.9 and 1.5 mug/mL, respectively. Manadomanzamines A and B also exhibit activities against human immunodeficiency virus (HIV-1) and AIDS opportunistic fungal infections.

Alkaloids↗

PubMed2002

Diversity and structure of the archaeal community in the leachate of a full-scale recirculating landfill as examined by direct 16S rRNA gene sequence retrieval.

The diversity and structure of the archaeal community in the effluent leachate from a full-scale recirculating landfill was characterized by direct 16S rRNA gene (16S rDNA) retrieval. Total-community DNA was extracted from the microbial assemblages in the landfill leachate, and archaeal 16S rDNAs were amplified with a universally conserved primer and an Archaea-specific primer. The amplification product was then used to construct a 16S rDNA clone library, and 70 randomly selected archaeal clones in the library were grouped by restriction fragment length polymorphism (RFLP) analysis. Sequencing and phylogenetic analysis of representatives from each unique RFLP type showed that the archaeal library was dominated by methanogen-like rDNAs. Represented in the kingdom of Euryarchaeota were phylotypes highly similar to the methanogenic genera Methanoculleus, Methanosarcina, Methanocorpusculum, Methanospirillum and Methanogenium, where the clone distribution was 48, 11, 3, 1 and 1, respectively. No sequences related to known Methanosaeta spp. were retrieved. Four rDNA clones were not affiliated with the known methanogenic Archaea, but instead, they were clustered with the uncultured archaeal sequences recently recovered from anaerobic habitats. Two chimeric sequences were identified among the clones analyzed.

Archaea↗

PubMed2006

Blooms of single bacterial species in a coastal lagoon of the southwestern Atlantic Ocean.

We investigated seasonal differences in community structure and activity (leucine incorporation) of the planktonic bacterial assemblage in the freshwater and brackish-water zones of a shallow coastal lagoon of the southwestern Atlantic Ocean. Alphaproteobacteria formed the dominant microbial group in both zones throughout the sampling period. After an intrusion of marine water, members of the SAR11 lineage became abundant in the brackish-water zone. These bacteria were apparently distributed over the lagoon during the following months until they constituted almost 30% of all prokaryotic cells at both sampling sites. At the first sampling date (March 2003) a single alphaproteobacterial species unrelated to SAR11, Sphingomonas echinoides, dominated the microbial assemblages in both zones of the lagoon concomitantly with a bloom of filamentous cyanobacteria. Pronounced maxima of leucine incorporation were observed once in each zone of the lagoon. In the freshwater zone, this highly active microbial assemblage was a mix of the typical bacteria lineages expected in aquatic systems. By contrast, a single bacterial genotype with >99% similarity to the facultative pathogen gammaproteobacterial species Stenotrophomonas maltophilia formed >90% of the bacterial assemblage (>10(7) cell ml(-1)) in the brackish-water zone at the time point of highest bacterial leucine incorporation. Moreover, these bacteria were equally dominant, albeit less active, in the freshwater zone. Thus, the pelagic zone of the studied lagoon harbored repeated short-term blooms of single bacterial species. This finding may have consequences for environmental protection.

Alphaproteobacteria↗

PubMed1995

Impact of Field Release of Genetically Modified Pseudomonas fluorescens on Indigenous Microbial Populations of Wheat.

In a field release experiment, an isolate of Pseudomonas fluorescens, which was chromosomally modified with two reporter gene cassettes (lacZY and Kan(supr)-xylE), was applied to spring wheat as a seed coating and subsequently as a foliar spray. The wild-type strain was isolated from the phylloplane of sugar beet but was found to be a common colonizer of both the rizosphere and phylloplane of wheat as well. The impact on the indigenous microbial populations resulting from release of this genetically modified microorganism (GMM) was compared with the impact of the unmodified, wild-type strain and a nontreated control until 1 month after harvest of the crop. The release of the P. fluorescens GMM and the unmodified, wild-type strain resulted in significant but transient perturbations of some of the culturable components of the indigenous microbial communities that inhabited the rhizosphere and phylloplane of wheat, but no significant perturbations of the indigenous culturable microbial populations in nonrhizosphere soil were found. Fast-growing organisms that did not produce resting structures (for example, fluorescent pseudomonads and yeasts) seemed to be most sensitive to perturbation. In terms of hazard and risk to the environment, the observed microbial perturbations that resulted from this GMM release may be considered minor for several reasons. First, the recombinant P. fluorescens strain caused changes that were, in general, not significantly different from those caused by the unmodified wild-type strain; second, perturbations resulting from bacterial inoculations were mainly small; and third, the release of bacteria had no obvious effects on plant growth and plant health.

Journal Article↗

PubMed2003

Biodiversity, community structural shifts, and biogeography of prokaryotes within Antarctic continental shelf sediment.

16S ribosomal DNA (rDNA) clone library analysis was conducted to assess prokaryotic diversity and community structural changes within a surficial sediment core obtained from an Antarctic continental shelf area (depth, 761 m) within the Mertz Glacier Polynya (MGP) region. Libraries were created from three separate horizons of the core (0- to 0.4-cm, 1.5- to 2.5-cm, and 20- to 21-cm depth positions). The results indicated that at the oxic sediment surface (depth, 0 to 0.4 cm) the microbial community appeared to be dominated by a small subset of potentially r-strategist (fast-growing, opportunistic) species, resulting in a lower-than-expected species richness of 442 operational taxonomic units (OTUs). At a depth of 1.5 to 2.5 cm, the species richness (1,128 OTUs) was much higher, with the community dominated by numerous gamma and delta proteobacterial phylotypes. At a depth of 20 to 21 cm, a clear decline in species richness (541 OTUs) occurred, accompanied by a larger number of more phylogenetically divergent phylotypes and a decline in the predominance of Proteobacteria. Based on rRNA and clonal abundance as well as sequence comparisons, syntrophic cycling of oxidized and reduced sulfur compounds appeared to be the dominant process in surficial MGP sediment, as phylotype groups putatively linked to these processes made up a large proportion of clones throughout the core. Between 18 and 65% of 16S rDNA phylotypes detected in a wide range of coastal and open ocean sediments possessed high levels of sequence similarity (>95%) with the MGP sediment phylotypes, indicating that many sediment prokaryote phylotype groups defined in this study are ubiquitous in marine sediment.

Antarctic Regions↗

PubMed2006

Environmental controls on denitrifying communities and denitrification rates: insights from molecular methods.

The advent of molecular techniques has improved our understanding of the microbial communities responsible for denitrification and is beginning to address their role in controlling denitrification processes. There is a large diversity of bacteria, archaea, and fungi capable of denitrification, and their community composition is structured by long-term environmental drivers. The range of temperature and moisture conditions, substrate availability, competition, and disturbances have long-lasting legacies on denitrifier community structure. These communities may differ in physiology, environmental tolerances to pH and O2, growth rate, and enzyme kinetics. Although factors such as O2, pH, C availability, and NO3- pools affect instantaneous rates, these drivers act through the biotic community. This review summarizes the results of molecular investigations of denitrifier communities in natural environments and provides a framework for developing future research for addressing connections between denitrifier community structure and function.

DNA, Archaeal↗

PubMed2001

Pollution-induced community tolerance and functional redundancy in a decomposer food web in metal-stressed soil.

Pollution may lead to the development of pollution-induced community tolerance (PICT) in a stressed community. We studied the presence of PICT in soil food webs using soil microcosms. Soil microcosms containing soil invertebrates and microbes were collected from polluted and unpolluted areas and exposed to a range of soil zinc concentrations. A pine seedling was planted in each microcosm to measure the effects of the origin of the community and Zn pollution on above-ground plant production. The effects of the treatments on nutrient content in the soil were also measured. The diversity of soil microarthropods and the soil's mineral nutrient content were low at the Zn-polluted site. We did not observe an increasing Zn tolerance among the soil organisms in the polluted soil. However, low population growth rates of soil invertebrates from the polluted site may indicate the deleterious effects on fitness of long-lasting pollution. In the soil from the nonpolluted site, Zn additions caused changes in the invertebrate food web structure. These changes were explained by the good physiological condition of the animals and their insensitivity to Zn. The fact that the food web structure in soil from the polluted site did not change can be used as a rough indicator of PICT. Structural stability is presumed by the lack of Zn-sensitive species at this site and the inability of populations to acclimate by altering their growth or reproduction patterns in response to changing soil conditions. Although microbial-based soil decomposer systems may have a high functional redundancy, our results indicate that metal stress at the polluted site exceeds the tolerance limits of the system. As a consequence, ecosystem function at this site is endangered. This study also shows that the evolution of metal tolerance by soil decomposer organisms may not be a common reaction to soil pollution, although changes of population and community structure indicated severe metal stress on organisms.

Adaptation, Physiological↗

PubMed1999

Isoprenoid quinones as biomarkers of microbial populations in the environment.

Isoprenoid quinones are lipid molecules present in all species of respiratory and photosynthetic microorganisms and exhibit marked structural variations depending upon the microbial taxon. Taking advantage of this, quinones have been used not only as chemotaxonomic markers in microbial systematics but also as good measures of microbial populations in the environment in terms of quantity, quality, and activity. Basically, this biomarker approach, called the quinone profile method, is applicable to all environmental samples from which an absolute amount of microbial biomass > or =10(9) cells can be collected. The quinone profile method allows good measurement of both fundamental and applied aspects of ecological and environmental microbiology. In particular, numerical cluster analyses of quinone profiles are useful for monitoring microbial population shifts in an ecosystem which is not amenable to conventional culture methods and molecular techniques. The combined use of molecular techniques and the quinone profile method in this research area should provide more accurate and reliable data regarding population dynamics and community structures.

Journal Article↗

PubMed2004

High-throughput techniques for analyzing complex bacterial communities.

A more complete understanding of microbial diversity and the environmental processes they control will require much more than a biotic inventory. It will require a deeper understanding of the basic features of systems organization and inter-population interactions. Communities, not total biomass, control net process rates driving the biogeochemical cycles sustaining the biosphere. Although the general patterns of macroorganismal diversity are relatively well known, spatial and temporal patterns of microorganismal diversity are essentially unknown. Having tools capable of resolving these patterns is a prerequisite to developing an understanding of the relationship between community structure and function. This talk discusses conceptual and technical developments that now provide the framework for systematically resolving temporal and spatial patterns of microorganisms and relating those patterns to processes at local and system levels. Of particular emphasis will be ongoing studies using highly parallel analyses with DNA microarrays for intensive monitoring of microbial populations in environmental systems. Although microarray technology is reasonably well established for studies of model organisms in well-defined laboratory settings, the application of this technology to environmental systems of uncharacterized diversity imposes additional demands on implementation; in particular, the requirement for optimized discrimination between target and non-target nucleic acids in complex, and undefined, mixtures. To increase the resolving power (information content) of our DNA microarray format, we are investigating the use of thermal dissociation of hybrids immobilized on individual array elements to resolve target and non-target sequences that differ by a single nucleotide. These studies, combined with specialized algorithms for optimizing the readout of the microarray should serve for informed environmental application. Initial studies have validated the general approach for analyses of sediment systems.

Bacteria↗

PubMed2001

Interpreting 16S rDNA T-RFLP Data: Application of Self-Organizing Maps and Principal Component Analysis to Describe Community Dynamics and Convergence.

Interpreting the large amount of data generated by rapid profiling techniques, such as T-RFLP, DGGE, and DNA arrays, is a difficult problem facing microbial ecologists. This study compares the ability of two very different ordination methods, principal component analysis (PCA) and self-organizing map neural networks (SOMs), to analyze 16S-DNA terminal restriction-fragment length polymorphism (T-RFLP) profiles from microbial communities in glucose-fed methanogenic bioreactors during startup and changes in operational parameters. Our goal was not only to identify which samples were similar, but also to decipher community dynamics and describe specific phylotypes, i.e., phylogenetically similar organisms, that behaved similarly in different reactors. Fifteen samples were taken over 56 volume changes from each of two bioreactors inoculated from river sediment (S2) and anaerobic digester sludge (M3) and from a well-established control reactor (R1). PCA of bacterial T-RFLP profiles indicated that both the S2 and M3 communities changed rapidly during the first nine volume changes, and then became relatively stable. PCA also showed that an HRT of 8 or 6 days had no effect on either reactor communtity, while an HRT of 2 days changed community structure significantly in both reactors. The SOM clustered the terminal restriction fragments according to when each fragment was most abundant in a reactor community, resulting in four clearly discernible groups. Thirteen fragments behaved similarly in both reactors, eight of which composed a significant proportion of the microbial community as judged by the relative abundance of the fragment in the T-RFLP profiles. Six Bacteria terminal restriction fragments shared between the two communities matched cloned 16S rDNA sequences from the reactors related to Spirochaeta, Aminobacterium, Thermotoga, and Clostridium species. Convergence also occurred within the acetoclastic methanogen community, resulting in a predominance of Methanosarcina siciliae-related organisms. The results demonstrate that both PCA and SOM analysis are useful in the analysis of T-RFLP data; however, the SOM was better at resolving patterns in more complex and variable data than PCA ordination.

Journal Article↗

PubMed1995

Ceftibuten: a review of antimicrobial activity, spectrum and other microbiologic features.

Ceftibuten is a new, orally administered cephalosporin with exceptional beta-lactamase stability and potency against commonly isolated Gram-negative pathogens. More than 90% of recent Enterobacteriaceae clinical isolates were inhibited by < or = 8 micrograms/ml of ceftibuten. In only five enteric species (Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, Morganella morganii, Serratia marcescens) were more than 15% of strains resistant (minimal inhibitory concentrations (MIC, with percent of strains inhibited in subscript numbers) > 16 micrograms/ml) to ceftibuten. Enteritis-producing bacteria such as Salmonella, Shigella, Escherichia coli and Yersinia were very ceftibuten-susceptible (MIC50 < or = 0.13 microgram/ml). Fastidious Gram-negative species causing respiratory tract or genital infections had very low ceftibuten MICs, including beta-lactamase-positive Haemophilus influenzae (MIC90 0.06 to 2 micrograms/ml), Moraxella catarrhalis (MIC90 0.25 to 4 micrograms/ml), and Neisseria gonorrhoeae (MIC90 0.015 to 0.5 microgram/ml). Beta-hemolytic streptococci and penicillin-susceptible pneumococci were also inhibited by ceftibuten. Staphylococci, enterococci, Pseudomonas species and Gram-negative anaerobic bacteria were generally resistant to ceftibuten. Ceftibuten has demonstrated bactericidal activity against susceptible pathogens, has high affinity for several lethal penicillin-binding proteins and possesses stability to common plasmid- or chromosomal-mediated beta-lactamases, including those enzymes that hydrolyze parenteral third generation cephalosporins. The microbiologic features for ceftibuten indicate its clinical potential as chemotherapy for community-acquired respiratory tract infections.

Bacteria↗

PubMed2006

Bacterial activity, community structure, and centimeter-scale spatial heterogeneity in contaminated soil.

In an anthropogenically disturbed soil (88% sand, 8% silt, 4% clay), 150-mg samples were studied to examine the fine-scale relationship of bacterial activity and community structure to heavy metal contaminants. The soils had been contaminated for over 40 years with aromatic solvents, Pb, and Cr. Samples from distances of <1, 5, 15, and 50 cm over a depth range of 40-90 cm underwent a sequential analysis to determine metabolic potential (from 14C glucose mineralization), bacterial community structure [using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)], and total extractable Pb and Cr levels. Metabolic potential varied by as much as 10,000-fold in samples <1 cm apart; log-log plots of metal concentration and microbial metabolic potential showed no correlation with each other. Overall, metal concentrations ranged from 9 to 29,000 mg kg(-1) for Pb and from 3 to 8500 mg kg(-1) for Cr with small zones of high contamination present. All regions exhibited variable metal concentrations, with some soil samples having 30-fold differences in metal concentration in sites <1 cm apart. Geostatistical analysis revealed a strong spatial dependence for all three parameters tested (metabolic activity, Pb, and Cr levels) with a range up to 30 cm. Kriging maps showed that in zones of high metal, the corresponding metabolic activity was low suggesting that metals negatively impacted the microbial community. PCR-DGGE analysis revealed that diverse communities were present in the soils with a random distribution of phylotypes throughout the sampling zones. These results suggest the presence of spatially isolated microbial communities within the soil profile.

Bacteria↗

PubMed2004

Sulfate-reducing bacteria in tubes constructed by the marine infaunal polychaete Diopatra cuprea.

Marine infaunal burrows and tubes greatly enhance solute transport between sediments and the overlying water column and are sites of elevated microbial activity. Biotic and abiotic controls of the compositions and activities of burrow and tube microbial communities are poorly understood. The microbial communities in tubes of the marine infaunal polychaete Diopatria cuprea collected from two different sediment habitats were examined. The bacterial communities in the tubes from a sandy sediment differed from those in the tubes from a muddy sediment. The difference in community structure also extended to the sulfate-reducing bacterial (SRB) assemblage, although it was not as pronounced for this functional group of species. PCR-amplified 16S rRNA gene sequences recovered from Diopatra tube SRB by clonal library construction and screening were all related to the family Desulfobacteriaceae. This finding was supported by phospholipid fatty acid analysis and by hybridization of 16S rRNA probes specific for members of the genera Desulfosarcina, Desulfobacter, Desulfobacterium, Desulfobotulus, Desulfococcus, and Desulfovibrio and some members of the genera Desulfomonas, Desulfuromonas, and Desulfomicrobium with 16S rRNA gene sequences resolved by denaturing gradient gel electrophoresis. Two of six SRB clones from the clone library were not detected in tubes from the sandy sediment. The habitat in which the D. cuprea tubes were constructed had a strong influence on the tube bacterial community as a whole, as well as on the SRB assemblage.

Animals↗

PubMed2005

Symbiotic fermentation, digesta passage, and gastrointestinal morphology in bullfrog tadpoles (Rana catesbeiana).

Relative to other herbivorous vertebrates, the nutritional ecology and digestive physiology of anuran larvae remain poorly understood. Our objective was to compare gut structure and inhabitants, digesta passage, and microbial fermentation in bullfrog tadpoles (Rana catesbeiana) to those in other herbivores. Bullfrog tadpole gastrointestinal tracts were long and voluminous, with an enlarged colon that harbored a diverse symbiotic community. The transit time for particulate markers passing through bullfrog tadpoles was 6 h, the median retention time was 8-10 h, and gut clearance was 10-14 h postingestion. Relatively high levels of short-chain fatty acids in the hindgut of tadpoles indicated active microbial fermentation in this gut region. This report represents the first account of gastrointestinal fermentation in the class Amphibia. On the basis of in vitro fermentation assays, we estimated that microbial fermentation in the hindgut provides 20% of the total daily energy requirement of bullfrog tadpoles. These tadpoles also exhibited coprophagy, a practice that provides important nutritive gains in other herbivores. The physiological and behavioral characteristics of these tadpoles are remarkably similar to those of other small-bodied, hindgut-fermenting vertebrates, suggesting convergent digestive strategies among a broad range of herbivorous taxa.

Animals↗

PubMed2025

Archaea produce peptidoglycan hydrolases that kill bacteria.

The social life of archaea is poorly understood. In particular, even though competition and conflict are common themes in microbial communities, there is scant evidence documenting antagonistic interactions between archaea and their abundant prokaryotic brethren: bacteria. Do archaea specifically target bacteria for destruction? If so, what molecular weaponry do they use? Here, we present an approach to infer antagonistic interactions between archaea and bacteria from genome sequence. We show that a large and diverse set of archaea encode peptidoglycan hydrolases, enzymes that recognize and cleave a structure-peptidoglycan-that is a ubiquitous component of bacterial cell walls but absent from archaea. We predict the bacterial targets of archaeal peptidoglycan hydrolases using a structural homology approach and demonstrate that the predicted target bacteria tend to inhabit a similar niche to the archaeal producer, indicative of ecologically relevant interactions. Using a heterologous expression system, we demonstrate that two peptidoglycan hydrolases from the halophilic archaeaon Halogranum salarium B-1 kill the halophilic bacterium Halalkalibacterium halodurans, a predicted target, and do so in a manner consistent with peptidoglycan hydrolase activity. Our results suggest that, even though the tools and rules of engagement remain largely unknown, archaeal-bacterial conflicts are likely common, and we present a roadmap for the discovery of additional antagonistic interactions between these two domains of life. Our work has implications for understanding mixed microbial communities that include archaea and suggests that archaea might represent a large untapped reservoir of novel antibacterials.

N-Acetylmuramoyl-L-alanine Amidase↗