Characterization of high density monolayers of the biofilm bacterium<i>Caulobacter crescentus</i>: Evaluating prospects for developing immobilized cell bioreactors

Smit, John; Sherwood, Christopher; Turner, Robin F. B.

doi:10.1139/w99-145

Cited by 24 publications

(20 citation statements)

References 34 publications

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“…In addition, this bacterium has been exploited as a platform for biotechnology development on the basis of ready genetic manipulation, ease of growth and its non-pathogenic nature. 15 The C. crescentus is a gram negative non-pathogenic aquatic bacterium that produces a hexagonally patterned para crystalline surface layer (S-layer) composed of a single 98 kDa protein species that comprises approximately 10-12% of total cellular protein. Since S layer protein assembles on the outside of the cell, it is a secreted protein that is non-covalently anchored to the cell surface via a specific smooth lipopolysaccharide.…”

Section: Introductionmentioning

confidence: 99%

Anti-tumor effects of the bacterium caulobacter crescentus in murine tumor models

Bhatnagar

Awasthi²,

Nomellini³

et al. 2006

Cancer Biology & Therapy

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Caulobacter crescentus is a gram negative, non-pathogenic bacterium, common in aquatic and soil environments. One feature of note is a protein surface layer (S-layer) composed of a single protein, organized as a self-assembled crystalline array that coats the bacterium. In the course of efforts to express cancer-associated peptides as genetic insertions into the S-layer, we noted a tumor suppressive effect of the unmodified bacterium. C. crescentus was examined for anti-tumor activity against three transplantable tumor mouse models: Lewis lung carcinoma cells transfected with the MUC1 gene in C57BL/6, murine mammary carcinoma (EMT-6) in BALB/c (both in prophylactic and therapeutic mode) and murine leukemia cells (L1210) in DBA2. Mice were immunized three times i.p. with C. crescentus (2 x 10 7 cells/mouse). In prophylactic mode, the mice were challenged with tumor cells two weeks after the last immunization. Immunization with live C. crescentus resulted in anti-tumor activity in all three transplantable tumor models, as measured by prolonged survival, reduced tumor mass or reduced number of lung nodules, compared to saline control groups. In the Lewis lung and the EMT-6 mammary carcinoma murine models the number of lung nodules as well as the tumor weight was lower in mice treated with C. crescentus, compared to the control group; for EMT-6, this was observed in prophylactic and therapeutic modes. In the murine leukemia and Lewis lung carcinoma models prolonged survival was observed in the groups of mice immunized with Caulobacters. In most cases the live C. crescentus cells were markedly more efficacious than heat killed or formalin fixed cells, despite the fact that they do not grow or persist in mice. The results suggest that C. crescentus may be a safe, bacterial immunomodulator for the treatment of tumors.

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Section: Introductionmentioning

confidence: 99%

Anti-tumor effects of the bacterium caulobacter crescentus in murine tumor models

Bhatnagar

Awasthi²,

Nomellini³

et al. 2006

Cancer Biology & Therapy

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“…The holdfast, composed in part of a polysaccharide containing N-acetylglucosamine, is essential for adhesion (20). All of the mutants identified so far that are completely deficient in surface adhesion lack detectable N-acetylglucosamine at the tip of the stalk (5,21,40,41); this indicates that the holdfast N-acetylglucosamine plays a critical role in adhesion. Even though the holdfast N-acetylglucosamine cannot be detected in swarmer cells (15), swarmer cells can attach to surfaces (15,23,30).…”

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confidence: 98%

Development of Surface Adhesion inCaulobacter crescentus

2004

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Caulobacter crescentus has a dimorphic life cycle composed of a motile stage and a sessile stage. In the sessile stage, C. crescentus is often found tightly attached to a surface through its adhesive holdfast. In this study, we examined the contribution of growth and external structures to the attachment of C. crescentus to abiotic surfaces. We show that the holdfast is essential but not sufficient for optimal attachment. Rather, adhesion in C. crescentus is a complex developmental process. We found that the attachment of C. crescentus to surfaces is cell cycle regulated and that growth or energy or both are essential for this process. The initial stage of attachment occurs in swarmer cells and is facilitated by flagellar motility and pili. Our results suggest that strong attachment is mediated by the synthesis of a holdfast as the swarmer cell differentiates into a stalked cell.Aquatic bacteria can live in both planktonic and sessile states. In the planktonic state, a bacterium is free to move throughout the environment to find nutrients. However, in nature, bacteria are predominantly found in the sessile state attached to surfaces where they form communities called biofilms (14,25). Biofilms are defined as matrix-enclosed bacterial populations adherent to each other and/or to surfaces or interfaces (7). Bacteria in a biofilm are more resistant to antibiotics and are able to form symbiotic relationships with other members of the biofilm community (4,6,22,46).The transition from a planktonic state to a sessile state is a developmental process involving different environmental cues and the coordination of various molecular pathways and extracellular structures (9, 25, 33). There are three stages of biofilm formation, early attachment, maturation, and detachment. Initially, bacteria are found swimming close to a surface until they are able to overcome surface tension and bind, forming a monolayer biofilm. This monolayer biofilm eventually becomes tightly packed with additional cells, and microcolonies begin to form. During the maturation stage, a three-dimensional structure emerges that is made up of a matrix of exopolysaccharide and cells. The last stage is that of detachment, where planktonic cells are released from the biofilm (25,43).Limited studies on a small number of ␥-proteobacteria have been conducted to determine the genetic pathways and structures that play a role in biofilm development. Three structures show interspecies importance: pili, flagella, and exopolysaccharides. Flagella and type IV pili facilitate early attachment events in Pseudomonas aeruginosa (26) and Vibrio cholerae El Tor (44). Exopolysaccharides play a role in the initial stages of biofilm development in V. cholerae El Tor (44) as well as V. cholerae O139 (45), and contribute to biofilm maturation in Escherichia coli (8). Although there are overlaps in the requirements for adhesion to surfaces, some requirements are not common to all bacteria. For example, unlike the bacteria discussed above, V. cholerae O139 does not require type IV ...

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“…They have been found in freshwater, seawater, soil (51), ground water (37), wastewater (36), deep-sea sediment (38), and a deep subsurface gold mine (19) and have been noted for their ability to survive in broad environmental habitats where contamination may be present (8,48). In addition, Caulobacter crescentus has been shown to form high-density biofilms with the potential for use in bioreactors for bioremediation (60) and has been used as a model organism to study cell cycle control (32,40,41). Previous knowledge of this organism, including its genome sequence (45), has provided new and extremely valuable tools to study genome-wide response to heavy metal stress.…”

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confidence: 99%

Whole-Genome Transcriptional Analysis of Heavy Metal Stresses in Caulobacter crescentus

et al. 2005

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The bacterium Caulobacter crescentus and related stalk bacterial species are known for their distinctive ability to live in low-nutrient environments, a characteristic of most heavy metal-contaminated sites. Caulobacter crescentus is a model organism for studying cell cycle regulation with well-developed genetics. We have identified the pathways responding to heavy-metal toxicity in C. crescentus to provide insights for the possible application of Caulobacter to environmental restoration. We exposed C. crescentus cells to four heavy metals (chromium, cadmium, selenium, and uranium) and analyzed genome-wide transcriptional activities postexposure using an Affymetrix GeneChip microarray. C. crescentus showed surprisingly high tolerance to uranium, a possible mechanism for which may be the formation of extracellular calcium-uranium-phosphate precipitates. The principal response to these metals was protection against oxidative stress (up-regulation of manganese-dependent superoxide dismutase sodA). Glutathione S-transferase, thioredoxin, glutaredoxins, and DNA repair enzymes responded most strongly to cadmium and chromate. The cadmium and chromium stress response also focused on reducing the intracellular metal concentration, with multiple efflux pumps employed to remove cadmium, while a sulfate transporter was down-regulated to reduce nonspecific uptake of chromium. Membrane proteins were also up-regulated in response to most of the metals tested. A two-component signal transduction system involved in the uranium response was identified. Several differentially regulated transcripts from regions previously not known to encode proteins were identified, demonstrating the advantage of evaluating the transcriptome by using whole-genome microarrays.Potentially hazardous levels of heavy metals have dispersed into subsurface sediment and groundwater in a number of metal-contaminated sites and represent a challenge for environmental restoration. Effective bioremediation of these sites requires knowledge of genetic pathways for resistance and biotransformation by component organisms within a microbial community. However, a comprehensive understanding of bacterial mechanisms of heavy metal toxicity and resistance has yet to be achieved. While many metals are essential to microbial function, heavy metals, i.e., most of those with a density above 5 g/cm 3 , have toxic effects on cellular metabolism (46). The majority of heavy metals are transition elements with incompletely filled d orbitals providing heavy metal cations which can form complex compounds with redox activity (46,70). Therefore, it is important to the health of the organism that the intracellular concentrations of heavy metal ions are tightly controlled. However, due to their structural and valence similarities to nontoxic metals, heavy metals are often transported into the cytoplasm through constitutively expressed nonspecific transport systems (46). As such, heavy metals invariably find their way into the cell. Once inside the cell, toxic effects of heavy metals...

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Characterization of high density monolayers of the biofilm bacteriumCaulobacter crescentus: Evaluating prospects for developing immobilized cell bioreactors

Cited by 24 publications

References 34 publications

Anti-tumor effects of the bacterium caulobacter crescentus in murine tumor models

Anti-tumor effects of the bacterium caulobacter crescentus in murine tumor models

Development of Surface Adhesion inCaulobacter crescentus

Whole-Genome Transcriptional Analysis of Heavy Metal Stresses in Caulobacter crescentus

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