Microbiology Blog: The weblog for microbiologists

Conference Update: New Zealand Microbiological Society

noreply@blogger.com (Blog owner) — Fri, 05 Feb 2010 18:40:00 +0000

November 30 - December 3, 2010 New Zealand Microbiological Society and New Zealand Society for Biochemistry and Molecular Biology joint meeting

Auckland, New Zealand Further information
This is a multidisciplinary conference generally attracting 200-300 delegates. Most participants are New Zealand-based, although the conference also has a range of renowned international plenary speakers, encompassing diverse fields such as medical microbiology, wine science, food microbiology, industrial microbiology, microbial ecology, systems biology and molecular evolution.
Suggested reading: Molecular Microbiology Books

Conference Update: Superbugs and Superdrugs

noreply@blogger.com (Blog owner) — Fri, 05 Feb 2010 18:39:00 +0000

March 17 - 18, 2010 12th Annual Superbugs and Superdrugs

London, UK Further information
Organized by SMI. Keynote address from Professor Peter Hawkey, Professor of Public Health Bacteriology, University of Birmingham and Health Protection Agency.
Suggested reading: Microbiology Books

Conference Update: International Papillomavirus Conference

noreply@blogger.com (Blog owner) — Fri, 05 Feb 2010 18:38:00 +0000

July 3 - 8, 2010 26th International Papillomavirus Conference and Workshops
Montreal, Canada Further information

HPV 2010. Twenty-Sixth Annual International Papillomavirus Conference and Clinical Workshop
Suggested reading: Papillomavirus Research: From Natural History To Vaccines and Beyond

Conference update: Microbial Ecology and Disease

noreply@blogger.com (Blog owner) — Fri, 05 Feb 2010 18:37:00 +0000

September 6 - 10, 2010 XXXIII International Congress of the Society for Microbial Ecology and Disease

Cruiseship Aegean Pearl, Greece Further information

1st Day,Medical Microbial Ecology; 2nd Day,Dental Microbial Ecology; 3rd Day,Nutrition, Probiotics, Food and Water Microbial Ecology Health Related 4th Day,Environmental Microbial Ecology. The cruise programme includes some of the most well known Greek Islands such as Cosmopolitan Myconos, Rhodes, Patmos, Crete, the fascinating island of Santorini and Ephesus and Kusadasi in Turkey.
Suggested reading: Environmental Molecular Microbiology

Evolution of Plastids

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:40:00 +0000

Photosynthesis is one of the most successful energy production strategies on the planet and has been co-opted numerous times throughout evolutionary history via the uptake and retention of photosynthetic cells by non-photosynthetic eukaryotic heterotrophs. Whereas the result of this process is clear, what is not settled is the mode and tempo of plastid movement among eukaryotes, particularly plastids of red algal derivation. Recent changes in our understanding of the relationships between eukaryotic supergroups have only served to complicate the picture further. Of particular interest is the evolution of plastids, the relationships among photosynthetic eukaryotes, the process of endosymbiogenesis and the variation in ways plastids have been modified to suit the light harvesting needs of their hosts. The understanding of all of these factors is an active field of continued research that will undoubtedly lead to further discoveries in the coming years read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

Microbial Phylogenetics: Horizontal Gene Transfer

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:39:00 +0000

Efforts to construct the tree of life take their conceptual motivation from Charles Darwin's theory of evolution. Until the advent of molecular biology, however, a universal tree of life was well beyond the scope of the data and methods of traditional organismal phylogeny. The rapid development of these methods and bodies of genetic sequence from the 1970s onwards resulted in major reclassifications of life and revived ambitions to represent all organismal lineages by one true tree of life. Subsequent realization of the significance of lateral gene transfer and other non-vertical processes has subtly reconceptualized and reoriented attempts to construct this universal phylogeny.
Gene transfer has affected the formation of groups of organisms. Gene transfer can make it more difficult to define and determine relationships. In those cases where many genes have been transferred between preferred partners, the majority of genes in a genome may reflect gene acquisition, and as a consequence, if a coherent signal is detected, one nevertheless might not be sure that the signal is due to organismal shared ancestry. However, the presence of a particular transferred gene has been shown, in several cases, to constitute a shared derived character useful in classification. Gene transfer can put together new metabolic pathways that open up new ecological niches, and consequently, the transfer of an adaptive gene might create a new group of organisms read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

Microbial Phylogenetics: Conserved Indels

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:37:00 +0000

Comparative analysis of genome sequences is leading to discovery of large numbers of novel molecular markers that are proving very helpful in understanding many important aspects of microbial phylogeny. Of these molecular markers, the conserved inserts or deletions (indels) in protein sequences provide particularly useful means for identifying different groups of microbes in clear molecular terms and for understanding how they have branched off from a common ancestor. Conserved indels and other novel molecular markers (viz. lineage-specific proteins) can be useful for understanding microbial phylogeny at different phylogenetic depths. Genetic and biochemical studies of these markers should also lead to identification of novel properties that are unique to different groups of microbes read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

Rooting the Tree of Life

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:36:00 +0000

Defining the evolutionary relationships between groups of organisms is a major part of modern-day microbiology. With the continuing dramatic increase in the availability of genomic data, these techniques have been extended to describing an all-encompassing "tree of life". However, identifying the location of the root of this tree corresponding to the most recent common ancestor is a challenging and distinct problem that has yet to be solved. To date, many investigations have proposed various roots, using a wide diversity of biological data and techniques. A survey of the most promising of these models illustrates the difficulty faced in reaching a scientific consensus on the issue, as well as the additional philosophical complications posed by our emerging understanding of the role of horizontal gene transfer in genome evolution read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

The Phyla of Prokaryotes

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:35:00 +0000

There is no official classification of prokaryotes. For the higher taxa there even is no official nomenclature: the rules of the International Code of Nomenclature of Prokaryotes do not cover taxa above the rank of class. The most commonly accepted division of the prokaryotes in two "subkingdoms" or "domains" (Bacteria and Archaea) and the classification of their species with validly published names in respectively 27 and 2 "phyla" or "divisions" (as of November 2009) is primarily based on 16S rRNA sequence comparisons. This type of classification was adopted in the latest edition of Bergey's Manual of Systematic Bacteriology. Alternative classifications have been proposed as well, based e.g. on the structure of the cell wall. Some 16S rRNA sequence-based phyla unite prokaryotes of similar physiological properties (for example Cyanobacteria, Chlorobi, Thermotogae); others (Euryarchaeota, Proteobacteria, Flavobacteria) contain organisms with highly disparate lifestyles. Some phyla based on deep 16S rRNA lineages are currently represented by one or a few species only. Environmental genomics/metagenomics approaches suggest existence of many more phyla based on the deep lineages of 16S rRNA gene sequences recovered. To obtain the organisms harboring these sequences and to study their properties is a major challenge of microbiology today read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

Microbial Phylogenetics: Global Markers

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:32:00 +0000

The introduction of comparative rRNA sequence analysis represents a major milestone in the history of microbiology. The current taxonomy of prokaryotes as well as modern probe and chip based identification methods are mainly based upon rRNA derived phylogenetic conclusions. Also of importance is single gene based phylogenetic inference and alternative global markers include elongation and initiation factors, RNA polymerase subunits, DNA gyrases, heat shock and recA proteins. Although the comparative analyses are hampered by the generally low phylogenetic information content, and different resolution power, and multiple copies of the individual markers, the domain and prokaryotic phyla concept is globally supported read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

Multilocus Sequence Analysis

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:29:00 +0000

Multilocus sequence analysis (MLSA) represents the novel standard in microbial molecular systematics. In this context, MLSA is implemented in a relatively straightforward way, consisting essentially in the concatenation of several sequence partitions for the same set of organisms, resulting in a "supermatrix" which is used to infer a phylogeny by means of distance-matrix or optimality criterion-based methods. This approach is expected to have an increased resolving power due to the large number of characters analyzed, and a lower sensitivity to the impact of conflicting signals (i.e. phylogenetic incongruence) that result from eventual horizontal gene transfer events. The strategies used to deal with multiple partitions can be grouped in three broad categories: the total evidence, separate analysis and combination approaches. The concatenation approach that dominates MLSAs in the microbial molecular systematics literature is known to systematists working with plants and animals as the "total molecular evidence" approach, and has been used to solve difficult phylogenetic questions such as the relationships among the major groups of cetaceans, that of microsporidia and fungi, or the phylogeny of major plant lineages. The total molecular evidence approach has been criticized because by directly concatenating all available sequence alignments, the evidence of conflicting phylogenetic signals in the different data partitions is lost along with the possibility to uncover the evolutionary processes that gave rise to such contradictory signals. The nature of these conflicts is varied, but in the microbial world the strongest conflicting signals often derive from the existence of horizontal gene transfer events in the dataset. If the individuals containing xenologous loci are not identified and removed from the supermatrix prior to phylogeny inference, the resulting hypothesis may be strongly distorted, since standard treeing methods assume a single underlying evolutionary history. Based on these arguments, the conditional data combination strategy is to be generally preferred in bacterial MLSA read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

Microbial Phylogenetics Methods

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:25:00 +0000

The purpose of phylogenetic analysis is to understand the past evolutionary path of organisms. Even though we will never know for certain the true phylogeny of any organism, phylogenetic analysis provides best assumptions, thereby providing a framework for various disciplines in microbiology. Due to the technological innovation of modern molecular biology and the rapid advancement in computational science, accurate inference of the phylogeny of a gene or organism seems possible in the near future. There has been a flood of nucleic acid sequence information, bioinformatic tools and phylogenetic inference methods in public domain databases, literature and worldwide web space. Phylogenetic analysis has long played a central role in basic microbiology, for example in taxonomy and ecology. In addition, more recently emerging fields of microbiology, including comparative genomics and phylogenomics, require substantial knowledge and understanding of phylogenetic analysis and computational skills to handle the large-scale data involved. Methods of phylogenetic analysis and relevant computer software tools lend accuracy, efficiency and availability to the task.
There are four steps in general phylogenetic analysis of molecular sequences: (i) selection of a suitable molecule or molecules (phylogenetic marker), (ii) acquisition of molecular sequences, (iii) multiple sequence alignment (MSA) and (iv) phylogenetic treeing and evaluation. The first step of phylogenetic analysis is to choose a suitable homologous part of the genomes to be compared. Mechanisms of molecular evolution include mutations, duplication of genes, reorganization of genomes, and genetic exchanges such as recombination, reassortment and lateral gene transfer. Although all of this information can be used to infer phylogenetic relationships of genes or organisms, information on mutations, including substitution, insertion, and deletion, is most frequently used in phylogeny reconstruction. The aim is to infer a correct organismal phylogeny, using orthologous genetic loci, in which common ancestry of two sequences can be traced back to a speciation event. Phylogeny using homologous genetic loci derived by gene duplication (paralogy) or related through lateral gene transfer (xenology), cannot reflect evolutionary history of organisms.
Once DNA sequence data are generated, they are subjected to a multiple sequence alignment process. This involves finding homologous sites, that is, positions derived from the same ancestral organism in the molecules under study. A set of sequences can be aligned with another by introducing "alignment gaps" (known in brief as "gaps"). In general, multiple sequence alignment starts by aligning a pair of sequences (pairwise alignment), and is then expanded to multiple sequences using various algorithms.
Many algorithms and computer programs have been developed in the last few decades for multiple sequence alignment, but the original Clustal series programs are still most widely used and produce reasonably good quality MSA for small data sets. For a large dataset, such as massive pyrosequencing reads, the MUSCLE program can generate good compromise between accuracy and speed. The MAFFT program utilizes several different algorithmic approaches and can be used for either small or very large datasets. There are also other computer programs developed for general multiple sequence alignment, but the above three have been most popular and are routinely used in publications in various microbiological disciplines read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

Microbial Phylogenetics: A Historical Overview

noreply@blogger.com (Blog owner) — Tue, 02 Feb 2010 14:19:00 +0000

When at the end of the 19th century information began to accumulate about the diversity within the bacterial world, scientists started to include the bacteria in phylogenetic schemes to explain how life on Earth may have developed. Some of the early phylogenetic trees of the prokaryote world were morphology-based; others were based on the then-current ideas on the presumed conditions on our planet at the time that life first developed. Around 1950 many leading microbiologists had become pessimistic with respect to the possibility of ever reconstructing bacterial phylogeny. The concept of the prokaryote-eukaryote dichotomy did little to clarify phylogenetic relationships. The developing technology of nucleic acid sequencing, together with the recognition that sequences of building blocks in informational macromolecules (nucleic acids, proteins) can be used as "molecular clocks" that contain historical information, led to the development of the three-domain model (Archaea - Bacteria - Eucarya) in the late 1970s, primarily based on small subunit ribosomal RNA sequence comparisons. The information currently accumulating from complete genome sequences of an ever increasing number of prokaryotes are now leading to further modifications of our views on microbial phylogeny read more ...

from Molecular Phylogeny of Microorganisms by Aharon Oren and R. Thane Papke (2010)

References

Potential Risks of Nanotechnology on Human Health

noreply@blogger.com (Blog owner) — Fri, 29 Jan 2010 14:13:00 +0000

The risk assessment of nanoparticles and nanomaterials is of key importance for the continuous development in the new field of nanotechnology. Humans are increasingly being exposed to nanoparticles and nanomaterials, placing stress on the development and validation of reproducible toxicity tests. Tests currently used include genotoxicity and cytotoxicity tests, and in vivo toxicity models. The unique characteristics of nanoparticles and nanomaterials are responsible for their toxicity and interaction with biological macromolecules within the human body. This may lead to the development of diseases and clinical disorders. A loss in cell viability and structure can also occur in exposed tissues as well as inflammation and granuloma formation. The future of nanotechnology depends on the responsible assessment of nanoparticles and nanomaterials read more ...

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Nanofibers for Water Treatment

noreply@blogger.com (Blog owner) — Fri, 29 Jan 2010 14:13:00 +0000

Electrospinning is a highly versatile technique that can be used to create ultrafine fibres of various polymers and other materials, with diameters ranging from a few micrometers down to tens of nanometres. The nonwoven webs of fibers formed through this process typically have high specific surface areas, nano-scale pore sizes, high and controllable porosity and extreme flexibility with regard to the materials used and modification of the surface chemistry of the fibres. A combination of these features is utilized in the application of electrospun nanofibres to a variety of water treatment applications, including filtration, solid phase extraction and reactive membranes read more ...

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Reverse Osmosis

noreply@blogger.com (Blog owner) — Fri, 29 Jan 2010 14:12:00 +0000

The membrane separation technologies of reverse osmosis (hyperfiltration) and nanofiltration are important in water treatment applications. Reverse osmosis is based on the basic principle of osmotic pressure, while nanofiltration makes use of molecule size for separation. Recent advances in the field of nanotechnology are opening a range of possibilities in membrane technologies. These include: new membrane preparation and cleaning methods, new surface and interior modification possibilities, the use of new nanostructured materials, and new characterization techniques read more ...

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Nanofiltration in Wastewater Treatment

noreply@blogger.com (Blog owner) — Fri, 29 Jan 2010 14:11:00 +0000

Nanofiltration is a new type of pressure driven membrane process and used between reverse osmosis and ultrafiltration membranes. The most different speciality of nanofiltration membranes is the higher rejection of multivalent ions than monovalent ions. Nanofiltration membranes are used in softening water, brackish water treatment, industrial wastewater treatment and reuse, product separation in the industry, salt recovery and recently desalination as two pass nanofiltration system read more ...

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Nanozymes in Biofilm Removal

noreply@blogger.com (Blog owner) — Fri, 29 Jan 2010 14:09:00 +0000

Sessile communities of bacteria encased in extracellular polymeric substances (EPS) are known as biofilms and causes serious problems in various areas, amongst other, the medical industry, industrial water settings, paper industry and food processing industry.

Although various methods of biofilm control exist, these methods are not without limitations and often fail to remove biofilms from surfaces. Biofilms often show reduced susceptibility to antimicrobials or chemicals and chemical by-products may be toxic to the environment, whereas mechanical methods may be labour intensive and expensive due to down-time required to clean the system. This has led to a great interest in the enzymatic degradation of biofilms. Enzymes are highly selective and disrupt the structural stability of the biofilm EPS matrix.

Various studies have focused on the enzymatic degradation of polysaccharides and proteins for biofilm detachment since these are the two dominant components of the EPS. Due to the structural role of proteins and polysaccharides in the EPS matrix, a combination of various proteases and polysaccharases may be successful in biofilm removal. The biodegradability and low toxicity of enzymes also make them attractive biofilm control agents. Regardless of all the advantages associated with enzymes, they also suffer from various drawbacks given that they are relatively expensive, show insufficient stability or activity under certain conditions, and cannot be reused. Various approaches are being used to increase the stability of enzymes, including enzyme modification, enzyme immobilization, protein engineering and medium engineering. Although these conventional methods have been used frequently to improve the stability of enzymes, various new techniques, such as self-immobilization of enzymes, the immobilization of enzymes on nano-scale structures and the production of single-enzyme nanoparticles, have been developed.

Self-immobilization of enzymes entails the cross-linking of enzyme molecules with each other and yields final preparations consisting of essentially pure proteins and high concentrations of enzyme per unit volume. The activity, stability and efficiency of immobilized enzymes can be improved by reducing the size of the enzyme-carrier. Nano-scale carrier materials allow for high enzyme loading per unit mass, catalytic recycling and a reduced loss of enzyme activity. Furthermore, enzymes can be stabilized by producing single-enzyme nanoparticles consisting of single-enzyme molecules surrounded by a porous organic-inorganic network of less than a few nanometers thick. All these new technologies of enzyme stabilization make enzymes even more attractive alternatives to other biofilm removal and control agents read more ...

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Nanobiocides in Water Purification

noreply@blogger.com (Blog owner) — Fri, 29 Jan 2010 14:09:00 +0000

Electrospun nanofibers and nanobiocides show potential in the improvement of water filtration membranes. Biofouling of membranes caused by the bacterial load in water reduces the quality of drinking water and has become a major problem. Several studies showed inhibition of these bacteria after exposure to nanofibers with functionalized surfaces. Nanobiocides such as metal nanoparticles and engineered nanomaterials are successfully incorporated into nanofibers showing high antimicrobial activity and stability in water read more ...

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Nanobiotechnology for the Detection of Microbial Pathogens

noreply@blogger.com (Blog owner) — Fri, 29 Jan 2010 14:08:00 +0000

An adequate supply of safe drinking water is one of the major prerequisites for a healthy life, but waterborne diseases is still a major cause of death in many parts of the world, particularly in young children, the elderly, or those with compromised immune systems. As the epidemiology of waterborne diseases is changing, there is a growing global public health concern about new and reemerging infectious diseases that are occurring through a complex interaction of social, economic, evolutionary, and ecological factors. An important challenge is therefore the rapid, specific and sensitive detection of waterborne pathogens. Presently, microbial tests are based essentially on time-consuming culture methods. However, newer enzymatic, immunological and genetic methods are being developed to replace and/or support classical approaches to microbial detection. Moreover, innovations in nanotechnology and nanosciences are having a significant impact in biodiagnostics, where a number of nanoparticle-based assays and nanodevices have been introduced for biomolecular detection read more ...

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Nanotechnology in Water Treatment: Applications and Emerging Opportunities

noreply@blogger.com (Blog owner) — Fri, 29 Jan 2010 14:07:00 +0000

Nanotechnology, the engineering and art of manipulating matter at the nanoscale (1-100 nm), offers the potential of novel nanomaterials for the treatment of surface water, groundwater and wastewater contaminated by toxic metal ions, organic and inorganic solutes and microorganisms. Due to their unique activity toward recalcitrant contaminants and application flexibility, many nanomaterials are under active research and development.

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Iron in Yeasts

noreply@blogger.com (Blog owner) — Thu, 28 Jan 2010 13:52:00 +0000

Yeasts take up iron by three main mechanisms. In the reductive uptake mechanism, specialized flavo-hemoproteins (Fre) dissociate extracellular ferric complexes by reduction involving trans-plasma membrane electron transfer. The resulting free iron is then imported by a high-affinity permease system (Ftr), coupled to a copper-dependent oxidase (Fet), which channels iron through the plasma membrane. As a consequence, iron uptake by this mechanism is dependent on the availability of copper. In the siderophore-mediated mechanism, siderophores excreted by the cells or produced by other bacterial or fungal species are taken up without prior dissociation, via specific, copper-independent high-affinity receptors. The iron is then dissociated from the siderophores intracellularly, probably by reduction. In the heme uptake mechanism, free heme or heme bound to hemoglobin is taken up as such, probably by endocytosis. Iron is released intracellularly after hydrolysis of the porphyrin ring catalyzed by heme oxygenase. Within the cell, iron is stored in vacuoles or in siderophores.

Iron can be mobilized from vacuoles by a reductive mechanism homologous to that found at the plasma membrane. Regulation of iron uptake and iron use are mediated by transcriptional regulators acting either as activators in iron-deficient conditions or as repressors in iron-rich conditions, according to the yeast species; these regulators thus adjust the iron uptake flux to the cell's requirements. In the baker's yeast, Saccharomyces cerevisiae, a post-transcriptional mechanism is active under low iron conditions, involving the degradation of RNAs encoding inessential iron-utilizing proteins. Other fungi have mechanisms serving a similar purpose at the transcriptional level. Studies in S. cerevisiae show that mitochondria are central to regulating cellular iron homeostasis, through the synthesis of iron-sulfur clusters.

Further reading: Iron Uptake and Homeostasis in Microorganisms

Iron in Staphylococci

noreply@blogger.com (Blog owner) — Thu, 28 Jan 2010 13:51:00 +0000

Staphylococcus aureus causes a significant amount of human morbidity and mortality. The ability of S. aureus to cause disease is dependent upon its acquisition of iron from the host. S. aureus can obtain iron from various sources during infection, including heme and transferrin. The most abundant iron source in humans is heme-iron bound by hemoglobin contained within erythrocytes. S. aureus is known to lyse erythrocytes through secretion of pore-forming toxins, providing access to host hemoglobin.

Proteins of the iron-regulated surface determinant (Isd) system bind host hemoproteins, remove the heme cofactor, and shuttle heme into the cytoplasm for use as a nutrient iron source. Deletion of Isd system components decreases staphylococcal virulence, underscoring the importance of heme-iron acquisition during infection. In addition to heme, S. aureus can utilize transferrin-iron through the secretion of siderophores. Several staphylococcal siderophores have been described, some of which have defined roles during the pathogenesis of staphylococcal infections. A greater understanding of staphylococcal iron acquisition may lead to the development of novel therapeutic strategies that target nutrient uptake and decrease the threat of this increasingly drug-resistant bacterial pathogen.

Further reading: Iron Uptake and Homeostasis in Microorganisms

Iron in Bacillus

noreply@blogger.com (Blog owner) — Thu, 28 Jan 2010 13:50:00 +0000

Bacillus subtilis is a metabolically versatile soil microbe and Gram-positive model organism that displays a sophisticated adaptive response to conditions of iron limitation. The endogenous siderophore of B. subtilis is bacillibactin, a trimeric catecholate siderophore similar in structure to enterobactin. In addition to bacillibactin, B. subtilis can obtain iron from several xenosiderophores, ferric citrate, heme, and through a newly discovered elemental iron permease.

The regulation of iron homeostasis in B. subtilis is complex and involves a ferric uptake regulator (Fur) protein as master regulator and at least two subsidiary regulatory systems. The most significant of these is an iron-sparing/prioritization response controlled by the small RNA FsrA and three auxiliary proteins (FbpABC). In addition, the bacillibactin uptake system is transcriptionally activated by an AraC family activator, Btr that directly senses bacillibactin. Iron uptake and homeostasis systems in B. anthracis and related organisms are largely similar to those in B. subtilis with some additional components. These include a second siderophore synthesis operon for petrobactin, which is important for virulence, and a more elaborate (or at least better understood) heme uptake system.

Further reading: Iron Uptake and Homeostasis in Microorganisms

Iron in Cyanobacteria

noreply@blogger.com (Blog owner) — Thu, 28 Jan 2010 13:49:00 +0000

Cyanobacteria are dependent on but can also be compromised by metals such as iron. On the one hand the demand for iron for photosystem functionality represents a challenge for the iron uptake machinery in iron limiting environments. On the other hand intoxication by iron causes a severe problem for growth and reproduction. To overcome this dilemma cyanobacteria have developed a regulatory network controlling iron uptake. They produce siderophores, which are distinct from that of other bacteria. Furthermore, the iron metabolism is linked to the nitrogen metabolism as documented for example in Anabaena sp. PCC 7120.

Further reading: Iron Uptake and Homeostasis in Microorganisms