The plant pathogenic fungus Fusarium oxysporum secretes an effector that is similar to a plant peptide hormone, underscoring the variety of mechanisms that plant pathogens have evolved to tamper with host physiology.
Plant pathogens cause devastating diseases of crop plants and threaten food security in an era of continuous population growth. Annual losses due to fungal and oomycete diseases amount to enough food calories to feed at least half a billion people. Understanding how plant pathogens infect and colonize plants should help to develop disease-resistant crops. It appears that plant pathogens are sophisticated manipulators of their hosts. They secrete effector molecules that alter host biological processes in a variety of ways, generally promoting the pathogen lifestyle. A new study by Masachis, Segorbe and colleagues describes a new mechanism by which plant pathogens interfere with plant physiology. They discovered that the root-infecting fungus F. oxysporum secretes a peptide similar to the plant regulatory peptide RALF (rapid alkalinization factor) to induce host tissue alkalinization and enhance plant colonization. This study demonstrates that in addition to secreting classical plant hormones (or mimics thereof), fungi have also evolved functional homologues of plant peptides to alter host cellular processes.
Microbial communities—microbiomes—are intricately linked to human health and critical ecosystem services. New technologies allow the rapid characterization of hundreds of samples at a time and provide a sweeping perspective on microbiome patterns. However, a systematic understanding of what determines microbiome diversity and composition and its implications for system functioning is still lacking. A focus on the phenotypic characteristics of microorganisms—their traits—offers a path for interpreting the growing amount of microbiome data. Indeed, a variety of trait-based approaches have been proposed for plants and animal communities, and this approach has helped to clarify the mechanisms underlying community assembly, diversity-process relationships, and ecosystem responses to environmental change.
Although there is a growing emphasis on microbial traits, the concept has not been fully appreciated in microbiology. However, a trait focus for microorganisms may present an even larger research opportunity than for macro-organisms. Not only do microorganisms play a central role in nutrient and energy cycling in most systems, but the techniques used to characterize microbiomes usually provide extensive molecular and phylogenetic information.
ADVANCES One major difference between macro- and microorganisms is the potential for horizontal gene transfer (HGT) in microbes. Higher rates of HGT mean that many microbial traits might be unrelated to the history of the vertically descended parts of the genome. If true, then the taxonomic composition of a microbiome might reveal little about the health or functioning of a system. We first review key aspects of microbial traits and then recent studies that document the distribution of microbial traits onto the tree of life. A synthesis of these studies reveals that, despite the promiscuity of HGT, microbial traits appear to be phylogenetically conserved, or not distributed randomly across the tree of life. Further, microbial traits appear to be conserved in a hierarchical fashion, possibly linked to their biochemical and genetic complexity. For instance, traits such as pH and salinity preference are relatively deeply conserved, such that taxa within deep clades tend to share the trait. In contrast, other traits like the ability to use simple carbon substrates or to take up organic phosphorus are shallowly conserved, and taxa share these traits only within small, shallow clades.
OUTLOOK The phylogenetic, trait-based framework that emerges offers a path to interpret microbiome variation and its connection to the health and functioning of environmental, engineered, and human systems. In particular, the taxonomic resolution of biogeographic patterns provides information about the traits under selection, even across entirely different systems. Parallels observed among human and free-living communities support this idea. For instance, microbial traits related to growth on different substrates (e.g., proteins, fats, and carbohydrates) in the human gut appear to be conserved at approximately the genus level, a resolution associated with the level of conservation of glycoside hydrolase genes in bacteria generally. A focus on two particular types of traits—response and effect traits—may also aid in microbiome management, whether that means maintaining human health or mitigating climate change impacts. Future work on microbial traits must consider three challenges: the influence of different trait measurements on cross-study comparisons; correlations between traits within and among microorganisms; and interactions among microbial traits, the environment, and other organisms. Our conclusions also have implications for the growing field of community phylogenetics beyond applications to microorganisms.
The human virome plays important roles in health and immunity. However, current methods for detecting viral infections and antiviral responses have limited throughput and coverage. Here, we present VirScan, a high-throughput method to comprehensively analyze antiviral antibodies using immunoprecipitation and massively parallel DNA sequencing of a bacteriophage library displaying proteome-wide peptides from all human viruses. We assayed over 108 antibody-peptide interactions in 569 humans across four continents, nearly doubling the number of previously established viral epitopes. We detected antibodies to an average of 10 viral species per person and 84 species in at least two individuals. Although rates of specific virus exposure were heterogeneous across populations, antibody responses targeted strongly conserved “public epitopes” for each virus, suggesting that they may elicit highly similar antibodies. VirScan is a powerful approach for studying interactions between the virome and the immune system.
Science 5 June 2015: Vol. 348 no. 6239 DOI: 10.1126/science.aaa0698RESEARCH ARTICLEComprehensive serological profiling of human populations using a synthetic human viromeGeorge J. Xu1,2,3,4,*, Tomasz Kula3,4,5,*, Qikai Xu3,4, Mamie Z. Li3,4, Suzanne D. Vernon6, Thumbi Ndung’u7,8,9,10,Kiat Ruxrungtham11, Jorge Sanchez12, Christian Brander13, Raymond T. Chung14, Kevin C. O’Connor15,Bruce Walker8,9, H. Benjamin Larman16, Stephen J. Elledge3,4,6,†
1Program in Biophysics, Harvard University, Cambridge, MA 02115, USA.2Harvard-Massachusetts Institute of Technology (MIT) Division of Health Sciences and Technology, Cambridge, MA 02139, USA.3Division of Genetics, Department of Medicine, Howard Hughes Medical Institute, Brigham and Women's Hospital, Boston, MA 02115, USA.4Department of Genetics, Harvard University Medical School, Boston, MA 02115, USA.5Program in Biological and Biomedical Sciences, Harvard University, Cambridge, MA 02115, USA.6Solve ME/CFS Initiative, Los Angeles, CA 90036, USA.7KwaZulu-Natal Research Institute for Tuberculosis and HIV, Nelson R. Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa.8HIV Pathogenesis Programme, Doris Duke Medical Research Institute, Nelson R. Mandela School of Medicine, Durban, South Africa.9Ragon Institute of Massachusetts General Hospital, MIT, and Harvard University, Cambridge, MA 02139, USA.10Max Planck Institute for Infection Biology, Chariteplatz, D-10117 Berlin, Germany.11Vaccine and Cellular Immunology Laboratory, Department of Medicine, Faculty of Medicine; and Chula-Vaccine Research Center, Chulalongkorn University, Bangkok, Thailand.12Asociación Civil IMPACTA Salud y Educación, Lima, Peru.13AIDS Research Institute-IrsiCaixa and AIDS Unit, Hospital Germans Trias i Pujol, Universitat Autònoma de Barcelona, Badalona, Spain Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.14Division of Gastroenterology, Massachusetts General Hospital, Boston, MA 02114, USA.15Department of Neurology, Yale School of Medicine, New Haven, CT 06520, USA.16Division of Immunology, Department of Pathology, Johns Hopkins University, Baltimore, MD 21205, USA.↵†Corresponding author. E-mail: firstname.lastname@example.org
In a new study, published in Nature this week, a research team led from Uppsala University in Sweden presents the discovery of a new microbe that represents a missing link in the evolution of complex life.
The new group of archaea was discovered in sediments along the Arctic Mid-Ocean Ridge A newly discovered life form could help resolve one of the most contentious conundrums in modern biology.All organisms on Earth are classified as either...
As decomposers, fungi are key players in recycling plant material in global carbon cycles. We hypothesized that genomes of early diverging fungi may have inherited pectinases from an ancestral species that had been able to extract nutrients from pectin-containing land plants and their algal allies (Streptophytes). We aimed to infer, based on pectinase gene expansions and on the organismal phylogeny, the geological timing of the plant-fungus association. We analyzed 40 fungal genomes, three of which, including Gonapodya prolifera, were sequenced for this study. In the organismal phylogeny from 136 housekeeping loci, Rozella diverged first from all other fungi. Gonapodya prolifera was included among the flagellated, predominantly aquatic fungal species in Chytridiomycota. Sister to the Chytridiomycota were the predominantly terrestrial fungi including zygomycota I and II, along with the ascomycetes and basidiomycetes that comprise Dikarya. The Gonapodya genome has 27 genes representing five of the seven classes of pectin-specific enzymes known from fungi. Most of these share a common ancestry with pectinases from Dikarya. Indicating functional as well as sequence similarity,Gonapodya, like many Dikarya, can use pectin as a carbon source for growth in pure culture. Shared pectinases of Dikarya and Gonapodyaprovide evidence that even ancient aquatic fungi had adapted to extract nutrients from the plants in the green lineage. This implies that 750 million years, the estimated maximum age of origin of the pectin-containing streptophytes represents a maximum age for the divergence of Chytridiomycota from the lineage including Dikarya.
Fungal cell walls play dynamic functions in interaction of fungi with their surroundings. In pathogenic fungi, the cell wall is the first structure to make physical contact with host cells. An important structural component of fungal cell walls is chitin, a well-known elicitor of immune responses in plants. Research into chitin perception has sparked since the chitin receptor from rice was cloned nearly a decade ago. Considering the widespread nature of chitin perception in plants, pathogens evidently evolved strategies to overcome detection, including alterations in the composition of cell walls, modification of their carbohydrate chains and secretion of effectors to provide cell wall protection or target host immune responses. Also non-pathogenic fungi contain chitin in their cell walls and are recipients of immune responses. Intriguingly, various mutualists employ chitin-derived signaling molecules to prepare their hosts for the mutualistic relationship. Research on the various types of interactions has revealed different molecular components that play crucial roles and, moreover, that various chitin-binding proteins contain dissimilar chitin-binding domains across species that differ in affinity and specificity. Considering the various strategies from microbes and hosts focused on chitin recognition, it is evident that this carbohydrate plays a central role in plant–fungus interactions.
Andrea Sánchez-Vallet , Jeroen R. Mesters , Bart P.H.J. Thomma
Barbecues may one day be fueled by propane renewably generated by microbes. That's because scientists have for the first time genetically engineered E. coli, a bacterium commonly found in the human gut, to make propane. If scientists can develop a way for photosynthetic bacteria to produce this gas the same way, then solar-powered generation of this biofuel could become a reality.
Renewable fuels made by microbes are typically liquids. This is a problem for two reasons. One, the liquids might poison the microbes generating them. Two, separating and purifying the fuel from the solution that the microbes are growing in can be complex and costly.
One alternative might be the commonplace fuel propane, which microbes could, in theory, generate as a gas for easy and immediate extraction, reducing any toxic effects it could have on the microorganisms.
Every inch of our body, inside and out, is oozing with bacteria. In fact, the human body carries 10 times the number of bacterial cells as human cells. Many are our friends, helping us digest food and fight off infections, for instance.
Distasteful as it sounds, the transplantation of fecal matter is more successful for treating Clostridium difficile infections than previously thought. The research, published in the open access journal Microbiome, reveals that healthy changes to a patient's microbiome are sustained for up to 21 weeks after transplant, and has implications for the regulation of the treatment.
Clostridium difficile infections are a growing problem, leading to recurrent cases of diarrhea and severe abdominal pain, with thousands of fatalities worldwide every year. The infection is thought to work by overrunning the intestinal microbiome - the ecosystem of microorganisms that maintain a healthy intestine.
Fecal microbiota transplantation was developed as a method of treating C. difficile infection, and is particularly successful in patients who suffer repeat infections. Fecal matter is collected from a donor, purified, mixed with a saline solution and placed in a patient, usually by colonoscopy.
Previous research has shown that the fecal microbiota of patients resembles that of the donor, but not much is known about the short and long term stability of fecal microbiota transplanted into recipients.
In this research, Michael Sadowsky and colleagues at the University of Minnesota collected fecal samples from four patients before and after their fecal transplants. Three patients received freshly prepared microbiota from fecal matter and one patient received fecal microbiota that had previously been frozen. All received fecal microbiota from the same pre-qualified donor.
The team compared the pre- and post-transplant fecal microbial communities from the four patients, as well as from 10 additional patients with recurring C. difficile infections, to the sequences of normal subjects described in the Human Microbiome Project. In addition, they looked at the changes in fecal bacterial composition in recipients over time, and compared this to the changes observed within samples from the donor.
Surprisingly, after transplantation, patient samples appeared to sustain changes in their microbiome for up to 21 weeks and remained within the spectrum of fecal microbiota characterized as healthy.
A human using mind control to activate the expression of a gene sounds like an improbable science fiction version of the Pied Piper story. In fact, it is a cutting edge fusion of cybernetics and synthetic biology--the brainchild of Martin Fussenegger at ETH Zurich—and may represent the future of drug therapy regimens automatically dictated by brain states.
A University of Otago researcher is part of an international team that has discovered that horizontal gene transfer (HGT) played a surprisingly large role in the evolution of primitive microbes known as archaea.
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