Andrew J Spiers

• PhD (Auckland), MSc, BSc
• Reader in Environmental and Molecular Microbiology at Abertay University

The evolutionary success of the novel Wrinkly Spreader (WS) genotypes in diversifying Pseudomonas fluorescens SBW25 populations in static liquid microcosms has been attributed to the greater availability of O(2) at the air-liquid (A-L) interface where the WS produces a physically cohesive-class biofilm. However, the importance of O(2) gradients in...

In radiating populations of Pseudomonas fluorescens SBW25, adaptive wrinkly spreader (WS) mutants are able to gain access to the air-liquid (A-L) interface of static liquid microcosms and achieve a significant competitive fitness advantage over other non-biofilm-forming competitors. Aerotaxis and flagella-based swimming allows SBW25 cells to move i...

Model bacterial biofilm systems suggest that bacteria produce one type of biofilm, which is then modified by environmental and physiological factors, although the diversification of developing populations might result in the appearance of adaptive mutants producing altered structures with improved fitness advantage. Here we compare the air-liquid (...

The establishment of O2 gradients in liquid columns by bacterial metabolic activity produces a spatially-structured environment. This produces a high-O2 region at the top that represents an un-occupied niche which could be colonised by biofilm-competent strains. We have used this to develop an experimental model system using soil-wash inocula and a...

Pseudomonas fluorescens SBW25 is a model soil- and plant-associated bacterium capable of forming a variety of air–liquid interface biofilms in experimental microcosms and on plant surfaces. Previous investigations have shown that cellulose is the primary structural matrix component in the robust and well-attached Wrinkly Spreader biofilm, as well a...

Introduction Periodontal diseases are known to be associated with polymicrobial biofilms and inflammasome activation. A deeper understanding of the subgingival cytological (micro) landscape, the role of extracellular DNA (eDNA) during periodontitis, and contribution of the host immune eDNA to inflammasome persistence, may improve our understanding...

Bacteria produce a variety of polysaccharides with functional roles in cell surface coating, surface and host interactions, and biofilms. We have identified an ‘Orphan’ bacterial cellulose synthase catalytic subunit (BcsA)-like protein found in four model pseudomonads, P. aeruginosa PA01, P. fluorescens SBW25, P. putida KT2440 and P. syringae pv. t...

Early Mortality Syndrome (EMS) has been a major problem for shrimp aquaculture in Southeast Asia due to its epizootic prevalence within the region since the first reported case in 2009. This study explores the application of halophilic marine bacilli isolated from coral mucus and their quorum-quenching abilities as potential biocontrol agents in aq...

Novel antibiotic combinations may act synergistically to inhibit the growth of multidrug-resistant bacterial pathogens but predicting which combination will be successful is difficult, and standard antimicrobial susceptibility testing may not identify important physiological differences between planktonic free-swimming and biofilm-protected surface...

The effect of four groups of biocides including alcohols, hydrogen peroxide, quaternary ammonium compounds, and polymeric guanidines were evaluated using PA and SA biofilms.

Novel antibiotic combinations may act synergistically to inhibit the growth of multidrug-resistant bacterial pathogens but predicting which will be successful is difficult, and standard antimicrobial susceptibility testing may not identify important physiological differences between planktonic free-swimming and biofilm-protected surface-attached se...

The choice of effective biocides used for routine hospital practice should consider the role of disinfectants in the maintenance and development of local resistome and how they might affect antibiotic resistance gene transfer within the hospital microbial population. Currently, there is little understanding of how different biocides contribute to e...

The choice of effective biocides used for routine hospital practice should consider the role of disinfectants in the maintenance and development of local resistome and how they might affect antibiotic resistance gene transfer within the hospital microbial population. Currently, there is little understanding of how different biocides contribute to e...

We are investigating characteristics associated with oil degradation amongst bacteria isolated from clean and hydrocarbon contaminated soils from Nigeria and the UK.Our focus has been to identify bacteria expressing surfactants following isolation on Pseudomonas selective (PSA-CFC) and non-selective nutrient media and investigate the nature of surf...

Static microcosms are a well-established system used to study the adaptive radiation of Pseudomonas fluorescens SBW25 and the adaptive biofilm-forming mutants known as the Wrinkly Spreaders (WS). We have developed this system to investigate selection within multi-species communities using a soil-wash inoculum dominated by biofilm-competent pseudomo...

Several model plants are known to respond to bacterial quorum sensing molecules with altered root growth and gene expression patterns and induced resistance to plant pathogens. These compounds may represent novel elicitors that could be applied as seed primers to enhance cereal crop resistance to pathogens and abiotic stress and to improve yields....

Several model plants are known to respond to bacterial quorum sensing molecules with altered root growth and gene expression patterns and induced resistance to plant pathogens. These compounds may represent novel elicitors that could be applied as seed primers to enhance cereal crop resistance to pathogens and abiotic stress and to improve yields....

Mosquito breeding sites were grouped into two different study zones (A and B) on the basis of human related activities taking place in and around the breeding sites. An. gambiae larvae collected from ecologically contrasting breeding sites were reared to adults in the laboratory. Adults from the F1 progeny were assayed for resistance against 4% DDT...

Simplified experimental systems, often referred to as microcosms, have played a central role in the development of modern ecological thinking on issues ranging from competitive exclusion to examination of spatial resources and competition mechanisms, with important model-driven insights to the field. It is widely recognized that soil architecture i...

Bacterial success in colonizing complex environments requires individual response to micro-scale conditions as well as community-level cooperation to produce large-scale structures such as biofilms. Connecting individual and community responses could be achieved by linking the intracellular sensory and regulatory systems mediated by bis-(3′-5′)-cyc...

Vector resistance to insecticides is a major challenge in the crusade towards effective malaria control. The issue of tolerance of An. gambiae to commonly used insecticides that were hitherto active against the An. gambiae population has necessitate further effort towards recognizing the biological factors in the insects that facilitates the resist...

Bacterial bio-surfactants have a wide range of biological functions and biotechnological applications. Previous analyses had suggested a limit to their reduction of aqueous liquid surface tensions (γMin), and here we confirm this in an analysis of 25 Pseudomonas spp. strains isolated from soil which produce high-strength surfactants that reduce sur...

Combined experimental evolutionary and molecular biology approaches have been used to investigate the adaptive radiation of Pseudomonas fluorescens SBW25 in static microcosms leading to the colonisation of the air-liquid interface by biofilm-forming mutants such as the Wrinkly Spreader. In these microcosms, the ecosystem engineering of the early wi...

Fig. S1 Mutations identified in evolved clones. Fig. S2 Bacterial sensitivity to phage infection. Table S1 The potential effects of community interactions on evolution of a focal species. Table S2 Genomic changes in response to evolution.

Bacteria engage in a complex network of ecological interactions, which includes mobile genetic elements (MGEs) such as phages and plasmids. These elements play a key role in microbial communities as vectors of horizontal gene transfer but can also be important sources of selection for their bacterial hosts. In natural communities bacteria are likel...

Although bacterial cellulose synthase (bcs) operons are widespread within the Proteobacteria phylum, subunits required for the partial-acetylation of the polymer appear to be restricted to a few γ-group soil, plant-associated and phytopathogenic pseudomonads, including Pseudomonas fluorescens SBW25 and several Pseudomonas syringae pathovars. Howeve...

Biosurfactants which reduce the surface or interfacial tension of liquids and act as emulsifiers, foaming and dispersing agents with low toxicity, are increasingly finding applications in biotechnology and driving the search for novel compounds for further exploitation. Potential biosurfactants sourced from bacteria are often selected first by qual...

Adaptive radiation in bacteria has been investigated using Wrinkly Spreaders (WS), a morphotype which colonises the air-liquid (A-L) interface of static microcosms by biofilm formation with a significant fitness advantage over competitors growing lower down in the O2-limited liquid column. Here, we investigate several environmental parameters which...

Malaria being the most important endemic protozoan disease in the tropics in terms of morbidity and mortality has attracted a continuous effort by researchers for it's control and prevention. Malaria vector control programs in Africa rely heavily on the use of pesticides for insecticide treated nets (ITN) and long lasting insecticides treated nets...

Conjugative plasmids play a vital role in bacterial adaptation through horizontal gene transfer. Explaining how plasmids persist in host populations however is difficult, given the high costs often associated with plasmid carriage. Compensatory evolution to ameliorate this cost can rescue plasmids from extinction. In a recently published study we s...

Fig. S1. Relative fitness of different plasmid‐bearing transconjugants when grown in competition with plasmid free. Several GmR‐labelled and SmR‐labelled transconjugants were tested under low, intermediate and high levels of mercury and relative fitness in KB was plotted as in Fig. 4. One randomly selected transconjugant (coloured in red) was chose...

Coevolution with bacteriophages is a major selective force shaping bacterial populations and communities. A variety of both environmental and genetic factors has been shown to influence the mode and tempo of bacteria-phage coevolution. Here, we test the effects that carriage of a large conjugative plasmid, pQBR103, had on antagonistic coevolution b...

Anopheles gambiae (An. gambiae) is the principal malaria vector in Africa, where vector control measures involve the use of insecticides. The development of insecticides resistance mitigates these approaches. Glutathione (GSH) is widely distributed among all living organisms and is associated with detoxification pathways, especially the Glutathione...

Plasmids drive genomic diversity in bacteria via horizontal gene transfer [1, 2]; nevertheless, explaining their survival in bacterial populations is challenging [3]. Theory predicts that irrespective of their net fitness effects, plasmids should be lost: when parasitic (costs outweigh benefits), plasmids should decline due to purifying selection [...

Unlabelled: Bacteriophages are a major cause of bacterial mortality and impose strong selection on natural bacterial populations, yet their effects on the dynamics of conjugative plasmids have rarely been tested. We combined experimental evolution, mathematical modeling, and individual-based simulations to explain how the ecological and population...

Experimental evolution studies are used to investigate bacterial adaptive radiation in simple microcosms. In the case of the Wrinkly Spreader, a class of biofilm-forming adaptive mutants of Pseudomonas fluorescens SBW25, the current paradigm is that they are only evolutionarily successful in static microcosms where they out-compete other lineages f...

Plasmids are important mobile elements that can facilitate genetic exchange and local adaptation within microbial communities. We compared the sequences of four co-occurring pQBR-family environmental mercury resistance plasmids and measured their effects on competitive fitness of a Pseudomonas fluorescens SBW25 host, which was isolated at the same...

Abstract Anopheles gambiae (An. gambiae) is the principal malaria vector in Africa, where vector control measures involve the use of insecticides. The development of insecticides resistance mitigates these approaches. Glutathione (GSH) is widely distributed among all living organisms, and is associated with detoxification pathways, especially the...

Abstract The recently developed transparent soil consists of particles of Nafion, a polymer with a low refractive index (RI), which is prepared by milling and chemical treatment for use as a soil analogue. After the addition of a RI-matched solution, confocal imaging can be carried out in vivo and without destructive sampling. In a previous study,...

Unlabelled: Bacteria produce a variety of biosurfactants capable of significantly reducing liquid (aqueous) surface tension (γ) with a range of biological roles and biotechnological uses. To determine the lowest achievable surface tension (γMin ), we tested a diverse collection of Pseudomonas-like isolates from contaminated soil and activated slud...

Vibrio parahaemolyticus is a significant cause of gastroenteritis resulting from the consumption of undercooked sea foods and often cause significant infections in shrimp aquaculture. Vibrio virulence is associated with biofilm formation and is regulated by N-acylated homoserine lactone (AHL)-mediated quorum sensing. In an attempt to reduce vibrio...

Understanding evolution is crucial to modern biology, but most teachers would assume that practical demonstrations of evolution in school laboratories are unfeasible. However, perhaps they have not heard of 'evolution in a test tube' and how Wrinkly Spreaders can form the basis for both practical demonstrations of bacterial evolution and further wo...

Pseudomonas fluorescens SBW25 forms a cellulose-based biofilm at the air-liquid interface of liquid microcosms without the apparent involvement of AHL-based quorum signalling typically associated with biofilm-formation in pseudomonads. However, we have recently identified in the SBW25 genome a potential AHL-synthase ( PFLU0008 ), and a AHL-dependen...

Pseudomonas fluorescens SBW25 forms a cellulose-based biofilm at the air-liquid interface of liquid microcosms without the apparent involvement of AHL-based quorum signalling typically associated with biofilm-formation in pseudomonads. However, we have recently identified in the SBW25 genome a potential AHL-synthase ( PFLU0008 ), and a AHL-dependen...

Experimental evolution studies have investigated adaptive radiation in static liquid microcosms using the environmental bacterium Pseudomonas fluorescens SBW25. In evolving populations a novel adaptive mutant known as the Wrinkly Spreader arises within days having significant fitness advantage over the ancestral strain. A molecular investigation of...

(From the Introduction) Bacterial cellulose was first isolated from the air-liquid (A-L) interface biofilm produced by Bacterium xylinum in 1886, an acetic acid bacterium strain which would probably now be recognised as Gluconacetobacter xylinus (formerly Acetobacter xylinum) or a related species. Over the following century, more acetic acid bacter...

The fast pace of scientific research often means that contemporary investigators are unaware of critical developments resulting from the work of previous generations of scientists. We were superficially aware of Sergei Winogradsky (1856 – 1953) through his columns, currently in teaching to illustrate aspects of microbial succession and community fu...

Microcosms have been used extensively to investigate ecological factors, evolutionary dynamics and the underlying molecular biology of adapting populations of bacteria in experimental evolution studies. One such experimental system has combined simple glass vials containing King’s B liquid growth medium with the model soil and plant-associated pseu...

The ability to colonise the surface of liquids has obvious advantages for bacteria and biofilm formation at the meniscus and air-liquid (A-L) interface is common amongst environmental pseudomonads. Bacteria from this genus also colonise raw meat and in this work the ability of these to produce biofilms was assessed. Sixty isolates were recovered fr...

Understanding of soil processes is essential for addressing the global issues of food security, disease transmission and climate change. However, techniques for observing soil biology are lacking. We present a heterogeneous, porous, transparent substrate for in situ 3D imaging of living plants and root-associated microorganisms using particles of t...

Snapshots of volume renderings of confocal scans of Arabidopsis thaliana roots expressing GFP in plasma membranes (grey) in transparent soil with sulphorhdamine-B-dyed particles (orange). A. Lateral root emerging from primary root. Scale bar represents 170 µm. B. Section of primary root and root hairs in contact with Nafion particle. Scale bar repr...

(MPG)

In situ 3D image of Arabidopsis thaliana root with emrging lateral root expressing GFP in plasma membranes (green) in transparent soil with sulphorhdamine-B-dyed particles (orange). (MPG)

In situ 3D image of branched Arabidopsis thaliana roots expressing GFP in plasma membranes (green) in transparent soil with sulphorhdamine-B-dyed particles (red). (MPG)

In situ 3D image of Arabidopsis thaliana root with root hairs expressing GFP in plasma membranes (green) with Nafion particle of transparent soil (orange). (MPG)

A key gap in environmental impact assessments of emerging contaminants is the change in biological activity of microorganisms exposed to toxic substances. Silver-nanoparticles are among the top cytotoxic nanomaterials suspected to threaten microbial functions of natural and engineered systems. In this study, a novel light-interference technique ter...

In January 2011, a review about teacher education in Scotland included 50 recommendations designed to improve the learning of young people in Scotland. A feature of the recommendations was enhancement of teacher education via new national initiatives and strengthened partnerships between schools, local authorities and universities. The Scottish Bac...

There is a body of research which asserts that exfiltration from urban sewers can be a major contributor to groundwater pollution. Test rig studies by the authors and others have demonstrated a capacity for defects in sewer systems to be partially self-sealing due to sewer sediments and associated solids, wall slimes and biofilm growth. This sealin...

Several biological roles have been demonstrated for surfactants expressed by soil and rhizosphere Pseudomonas spp., but the impact of these powerful surface-active agents on the local soil-water distribution within the partially saturated soil pore network has not been examined. To investigate this potential hydrological role, the liquid surface te...

The aim of this work was to investigate the use of PET (polyethylene terephtalate) films as a modern development of Cholodny’s glass slides, to enable microscopy and molecular-based analysis of soil communities where spatial detail at the scale of microbial habitats is essential to understand microbial associations and interactions in this complex...

Understanding evolutionary mechanisms is fundamental to a balanced biological education, yet practical demonstra- tions are rarely considered. In this paper we describe a bacterial liquid microcosm which can be used to demonstrate aspects of evolution, namely adaptive radiation, niche colonisation and competitive fitness. In microcosms inoculated w...

Introduction Phytosphere is a complex environment for microorganisms of different groups1,2. The functional activity of microorganisms in a micro-community associated with a plant is defined as complex cellular interactions in a specific phyto-nishe3,4,5. The identification of cultivated and uncultivated microorganisms via microbiological and mole...

The Red Queen hypothesis proposes that coevolution of interacting species (such as hosts and parasites) should drive molecular evolution through continual natural selection for adaptation and counter-adaptation. Although the divergence observed at some host-resistance and parasite-infectivity genes is consistent with this, the long time periods typ...

(In Ukrainian) A link between rhizo-, phyllo-, and endospheres, the different components of the phytosphere of Brassica napus L. (rapeseed), has been studied with the model bacterium Pseudomonas fluorescens SBW25, under both sterile and non-sterile soil conditions, using both direct CLSM of plant tissues and the quasisubstratum approach. This metho...

Pseudomonas fluorescens are common soil bacteria that can improve plant health through nutrient cycling, pathogen antagonism and induction of plant defenses. The genome sequences of strains SBW25 and Pf0-1 were determined and compared to each other and with P. fluorescens Pf-5. A functional genomic in vivo expression technology (IVET) screen provid...

Pseudomonads are able to form a variety of biofilms that colonize the air-liquid (A-L) interface of static liquid microcosms, and differ in matrix composition, strength, resilience and degrees of attachment to the microcosm walls. From Pseudomonas fluorescens SBW25, mutants have evolved during prolonged adaptation-evolution experiments which produc...

Pseudomonas fluorescens are common soil bacteria that can improve plant health through nutrient cycling, pathogen antagonism and induction of plant defenses. The genome sequences of strains SBW25 and Pf0-1 were determined and compared to each other and with P. fluorescens Pf-5. A functional genomic in vivo expression technology (IVET) screen provid...

Effective gene trapping and screening requires sensory and regulatory compatibility of both host and exogenous systems. The naturally competent bacterium Acinetobacter baylyi ADP1 is able to efficiently take up and integrate exogenous DNA into the chromosome, making it an attractive host system for a wide range of metagenomic applications. To test...

With the quantity of genomic data increasing at an exponential rate, it is imperative that these data be captured electronically, in a standard format. Standardization activities must proceed within the auspices of open-access and international working bodies. To tackle the issues surrounding the development of better descriptions of genomic invest...

In a handful of fertile soil there are billions of microorganisms and yet, even with a conservative estimate, the surface area covered by these organisms is considerably less than 1%. What does this tell us about the function of the physical structure in which soil organisms reside and function, collecting, and separating micropopulations from each...

The plasmid pQBR103 was found within Pseudomonas populations colonizing the leaf and root surfaces of sugar beet plants growing at Wytham, Oxfordshire, UK. At 425 kb it is the largest self-transmissible plasmid yet sequenced from the phytosphere. It is known to enhance the competitive fitness of its host, and parts of the plasmid are known to be ac...

Understanding the connections among genotype, phenotype, and fitness through evolutionary time is a central goal of evolutionary genetics. Wrinkly spreader (WS) genotypes evolve repeatedly in model Pseudomonas populations and show substantial morphological and fitness differences. Previous work identified genes contributing to the evolutionary succ...

Although plasmids are ubiquitous amongst phytosphere pseudomonads, the advantage and costs of plasmids for the bacterial host remain unclear. The application of single-cell Raman spectral analysis to plasmid-bacterial systems under different environmental conditions offers a new means of determining the impact of plasmids on host cell physiology, m...

The GGDEF response regulator WspR couples the chemosensory Wsp pathway to the overproduction of acetylated cellulose and cell attachment in the Pseudomonas fluorescens SBW25 wrinkly spreader (WS) genotype. Here, it is shown that WspR is a diguanylate cyclase (DGC), and that DGC activity is elevated in the WS genotype compared to that in the ancestr...

Biofilms, and other bacterial aggregations, are of significance in both environmental microbiology and in plant and human pathogenesis. Comparative single-cell Raman spectral analysis can differentiate between planktonic bacteria and those recovered from biofilms and appears to offer a new means by which to investigate bacterial cell physiology, me...

Single-cell Raman microspectroscopy has the potential to report on the whole-cell chemical composition of bacteria, reflecting metabolic status as well as growth history. This potential has been demonstrated through the discriminant functional analysis of Raman spectral profiles (RSP) obtained from the soil and plant-associated bacterium Pseudomona...