Type IV secretion systems are multiprotein complexes that mediate the translocation of macromolecules (proteins, DNA or DNA-protein complexes) across the bacterial cell envelope into the extracellular medium or directly into recipient cells. This strategy is exploited for the delivery of effector molecules that modulate host cell interactions by bacterial pathogens and symbionts. Type IV secretion systems also mediate the translocation of DNA molecules from bacteria and the uptake of DNA into bacteria and thereby contribute to horizontal gene transfer.

The term type IV secretion system (T4SS) was originally based on the significant sequence similarities between the protein components of macromolecular transporters used for plasmid transfer and for the delivery of virulence factors from bacterial pathogens to their hosts. The two first examples that prompted the proposal of T4SSs as a distinct family of macromolecular transporters were the conjugative plasmid RP4 transfer machinery (Trb) and the VirB/D4 machinery used by the plant pathogen Agrobacterium tumefaciens for the delivery of single-stranded DNA and of protein virulence factors to plants.

T4SSs carry out one of three functions. The first group of T4SSs translocates exclusively DNA and serves for the uptake or secretion of genetic information. The second group translocates DNA molecules as well as proteins from donor to recipient cells. The third group exclusively translocates proteins and those are either secreted into the exterior medium or directly into recipient cells.

Since the original proposal that T4SS constitute a distinct class of secretion systems was made, the number of known T4SS has continued to grow and both metagenomic as well as functional analyses continue to add new examples. Since many T4SSs localize on plasmids they can be transmitted by horizontal gene transfer and this has very interesting implications for their evolution.

from Christian Baron in Bacterial Secreted Proteins

Further reading:

1. Bacterial Secreted Proteins: Secretory Mechanisms and Role in Pathogenesis
2. Microbiology Books

Labels: bacteria, protein, protein secretion, proteins

The peptidoglycan or murein sacculus is the stress-bearing structure of bacterial cells. It consists of glycan strands cross-linked by peptide bridges. Even though studies on murein have a very long tradition, it is not known how the glycan strands are actually arranged.

The chemical fine structure and the muropeptide composition of different Gram-negative and Gram-positive bacteria have been investigated in detail. Escherichia coli and Staphylococcus aureus are generally considered representatives for both Gram forms. During cell growth the stress-bearing structure has to be elongated and/or divided by the insertion of new and elimination of old material without losing its strength. Therefore multienzyme complexes containing both murein synthases and murein hydrolases have been postulated.

Peptidoglycan biosynthesis is the target for many antibiotics such as β-lactams, D-cycloserine and glycopeptide-antibiotics such as vancomycin. Bacteria have developed a number of different strategies for coping with antibiotic and osmotic stress.

from Ute Bertsche in Bacterial Polysaccharides: Current Innovations and Future Trends

Further reading:

1. Bacterial Polysaccharides
2. Microbial Production of Biopolymers and Polymer Precursors
3. Microbiology Books

Labels: antibiotic resistance, biopolymers, peptidoglycan, polysaccharides

The type-III secretion system (T3SS) is an export machine used by pathogenic Gram-negative bacteria to deliver proteins straight into the eukaryotic cytosol with the aim to subvert the host cell defense. After the discovery of T3S in 1990, significant progress has been made in the understanding of its structure, assembly and function. The basic structure consisting of the membrane-embedded basal body, the needle and the tip structure has been analyzed in more detail. The composition of several structural components has been determined and important insights into the assembly process have been gained. The relationship between the T3SS of pathogenic bacteria and the flagellum has been noted. Besides the structural similarities, the assembly of these two nanomachines shows some commonalities, for example the length control of external structures such as the T3 needle and the flagellar hook. The T3SS also includes the pore forming translocator proteins, effector proteins and a set of specific chaperones. A recent review on the type-III secretion system focuses on the structure and assembly of this fascinating nanomachine.

from Sorg and Cornelis in Bacterial Secreted Proteins

Further reading:

1. Bacterial Secreted Proteins: Secretory Mechanisms and Role in Pathogenesis
2. Microbiology Books

Labels: bacteria, protein, protein secretion, proteins

Writing in a recent issue of "Microbiology Today", Norman Fry of the Health Protection Agency, UK reviews a book on Legionella published by Caister Academic Press:

"The first three chapters of this book provide general introductions to the field. The excellent opening chapter on history and clinical findings provides comprehensive and fascinating insights into LD ... (other chapters) describe in detail the unique nature of legionella as intracellular parasite, its ability to infect macrophages and its extracellular lifestyle. There are also comprehensive reviews on the flagellar system, genomics, secretion, export, survival mechanisms including Dot/Icm, nutrient acquisition and assimilation strategies and the use of L. pneumophila as a model organism. Overall the book is good series of expert reviews ... providing a useful state-of-the-art reference"

Legionella: Molecular Microbiology
Publisher: Caister Academic Press
Edited by: Klaus Heuner and Michele Swanson
Publication date: March 2008
ISBN: 978-1-904455-26-4
Price: GB £150 or US $300 (hardback).
Pages: x + 249 + colour plate

Further reading: Legionella: Molecular Microbiology

Labels: book review, legionella

Gram-negative bacteria have evolved several secretory pathways to release proteins or toxic factors into their surrounding environment. Many virulence determinants, including extracellular toxins and proteases, are secreted by the type II secretion system (T2SS) which is widely conserved and common among γ-proteobacteria.

Typical T2SSs are composed of 12 to 16 proteins termed Gsp (General secretion pathway) proteins. These components associate in a multiprotein complex that constitutes a large structure (the secreton) that spans the periplasm and is thought to connect inner and outer membranes. Exoproteins that use the T2SS are characterized by the presence of a leader peptide (or signal peptide) at their N terminus and are secreted in the extracellular medium by a two-step process involving a transient periplasmic intermediate. The T2SS is unique in its ability to promote secretion of large multimeric proteins that are folded in the periplasm. The system is also characterized by a species-specificity, which is mainly related to the GspC and GspD components, the gatekeepers.

Although relatively little attention has been payed to the regulation of T2SSs, it was observed that expression of most of the genes encoding T2SS-dependent exoproteins is growth phase-dependent or strictly regulated by environmental signals. In Pseudomonas aeruginosa, T2SS assembly and most of the T2SS-dependent exoproteins are regulated via quorum sensing, a mechanism that senses the density of a surrounding bacterial population.

Besides typical T2SSs, some secretory systems are found which contain all the T2SS components but in a different genetic organization. Some incomplete systems have also been described which contain genes homologous to T2SS but dispersed on the bacterial chromosome. Components of these systems can either associate with classical T2SS components to constitute a functional hybrid machinery or represent peculiar systems with strictly defined functions.

from Michel and Voulhoux in Bacterial Secreted Proteins

Further reading:

1. Bacterial Secreted Proteins: Secretory Mechanisms and Role in Pathogenesis
2. Pseudomonas: Genomics and Molecular Biology
3. Microbial Toxins: Current Research and Future Trends

Labels: bacteria, protein, protein secretion, proteins, Pseudomonas, toxin

Writting in the latest issue of the ISPP Newsletter published by the International Society for Plant Pathology, Chris Hayward describes the new book on Plant Pathogenic Bacteria from Caister Academic Press as:

"... comprehensive in coverage ... This book is a timely addition to the literature in a rapidly expanding field which provides ample evidence of hypothesis testing on a broad front."

Further reading: Plant Pathogenic Bacteria: Genomics and Molecular Biology

Labels: bacteria, book review, plant

A list of conferences, meetings, symposia and workshops relating to all aspects of mycology, yeast and fungal science and medicine.

February 1 - 14, 2009. Comparative analysis of in vitro and in vivo Candida albicans-host interaction systems
Madrid, Spain Further information
Federation of European Biochemical Societies advanced practical and lecture course. The aim of this two-week course is to introduce students to the latest techniques of in vivo infection and ex-vivo/in vitro interaction models between the human pathogen Candida albicans and the host.
Suggested reading: Candida Book

March 17 - 22, 2009. 25th Fungal Genetics Conference
Asilomar, California, USA Further information
Billed as the biggest worldwide conference on genetics of filamentous fungi.
Suggested reading: Aspergillus: Molecular Biology and Genomics

March 29 - 31, 2009. British Society for Medical Mycology (BSMM) Annual Scientific Meeting
Imperial College London, UK Further information
Translational Research in Medical Mycology
Suggested reading: Mycology Books

April 6 - 7, 2009. Economic and Social Impact of Fungal Deteriogens
Manchester, UK Further information
Organised by the British Mycological Society and the International Biodeterioration and Biodegradation Society. Session titles include: Fungal Deteriogen of Materials and their Conservation, Fungal Deteriogens and Food Spoilage, Impact of Fungal Deteriogens on Health, Economic Impact of Fungal Deteriogens. In addition there will be a number of posters.
Suggested reading: Microbial Biodegradation: Genomics and Molecular Biology and Mycology books

May 25 - 29, 2009. The 17th Congress of The International Society for Human and Animal Mycology 2009 (ISHAM 2009)
Keio Plaza Hotel, Shinjuku, Tokyo, Japan Further information
ISHAM2009 will address recent developments in medical, veterinary and environmental mycology with a focus on human and animal health. More than 30 symposia with distinguished speakers are planned, including keynote lectures, luncheon and evening seminars, and a new Poster Forum.
Suggested reading: Mycology Books

June 21 - 26, 2009 Mycotoxins and Phycotoxins
New London, NH, USA Further information
Gordon Research Conference. Presentation of leading-edge research on fungal, algal, and cyanobacterial toxins and the organisms that produce them. This multidisciplinary gathering will encompass the biology, ecology, genetics, chemistry and the public health and economic impacts
Suggested reading: Aspergillus: Molecular Biology and Genomics

July 19 - 24, 2009. 24th International Conference on Yeast Genetics and Molecular Biology
Manchester, UK Further information
Key conference themes will include: Cell Cycle and Morphogenesis, Control of Gene Expression, Genomes and Evolution, Protein Trafficking, Signal Transduction, Systems Biology, Yeasts as Cell Factories, Yeasts as Models for Ageing and Human Disease, Yeasts as Pathogens
Suggested reading: Mycology Books

August 26 - 29, 2009. Pasteur's Legacy: Yeast for Health and Biotechnologies (the 27th International Specialised Symposium on Yeast)
Institut Pasteur, Paris, France Further information

September 1 - 4, 2009. British Mycological Society annual scientific meeting
Dundee, UK Further information
The Fungal Cell. Including cellular organisation, metabolism and cellular regulation, fungal growth, morphogenesis and differentiation, and fungal interactions with other organisms including bacteria and plants.
Suggested reading: Mycology Books

October 18 - 21, 2009. 4th Trends in Medical Mycology TIMM4
Athens, Greece Further information
Organized jointly by the European Confederation of Medical Mycology (ECMM) and by the Infectious Diseases Group of the European Organization for Research and Treatment of Cancer (IDG-EORTC). The scientific programme will include plenary sessions on fungal infections in both immunocompromised and immunocompetent hosts led by an internationally renowned faculty giving plenary talks, round table sessions, and meet-the-expert meetings. The poster session will encourage one-to-one discussions between faculty, presenters and delegates. The meeting is designed for infectious disease specialists, haematologists, oncologists, transplant physicians, microbiologists, immunologists, dermatologists, intensivists and others with interest in medical mycology.
Suggested reading: Mycology Books

October 29 - 31, 2009. Mycology MasterClass IV
Hamilton Island, QLD, Australia Further information
Advanced medical mycology course for specialists and trainees in infectious diseases, microbiology, haematology and intensive care medicine and for laboratory scientists/technicians specialising in medical mycology.
Suggested reading: Aspergillus: Molecular Biology and Genomics

Labels: aspergillus, conference, fungal, fungi, mycology, yeast

Writing in a recent issue of "Legionella Enews", Matt Freije reviews a book on Legionella published by Caister Academic Press:

"This book is a must for microbiologists involved with Legionella ... it will make a nice addition to the library of anyone professionally involved with Legionnaires' disease and Legionella bacteria."

Legionella: Molecular Microbiology
Publisher: Caister Academic Press
Edited by: Klaus Heuner and Michele Swanson
Publication date: March 2008
ISBN: 978-1-904455-26-4
Price: GB £150 or US $300 (hardback).
Pages: x + 249 + colour plate

Further reading: Legionella: Molecular Microbiology

Labels: book review, legionella

October 22 - 23, 2009. European Meeting on Molecular Diagnostics
Scheveningen, The Hague, Netherlands Further information
The sixth in a series of meetings, devoted to all aspects of molecular diagnostics in disease and pathology of humans. The Scheveningen Meeting is organised every two years. The scope of the meeting has expanded to include other amplification techniques, general probe technology and more laboratory disciplines. The emphasis of the meetings will continue to be on novel technology and its consequences for (new) clinical molecular diagnostics. The format of the meetings includes general, introductory lectures by internationally renowned experts in combination with free presentations in dedicated workshops, poster session and industrial exhibits.
Suggested reading: Real-Time PCR in Microbiology

Labels: conference

June 15 - 19, 2009. The 10th International Symposium on Bacterial Genetics and Ecology
Uppsala, Sweden Further information
Coexisting on a Changing Planet. The 10th BAGECO conference will focus on bacteria in the world around us, and the implications of a changing climate and other anthropogenic influences on bacterial genetics and ecology. Climate change is now accepted as a serious challenge to global ecosystems, but the extent of its impact on bacterial communities has only begun to be explored.

Labels: conference