MicrobiologyBytes

Four new fungi in the genus Ophiocordyceps have been identified. These fungi belong to a group of “zombifying” fungi that infect ants and then manipulate their behavior, eventually killing the ants after securing a prime location for spore dispersal.

Beyond this important milestone, the paper also draws attention to undiscovered, complex, biological interactions in threatened habitats. The four new species all come from the Atlantic Rainforest of Brazil which is the most heavily degraded biodiversity hotspot on the planet. Ninety-two percent of its original coverage is gone. The effect of biodiversity loss on community structure is well known. What researchers don’t know is how parasites, such as these zombie-inducing fungi, cope with fragmentation. The authors show that each of the four species is highly specialized on one ant species and has a suite of adaptations and spore types to ensure infection. The life-cycle of these fungi that infect, manipulate and kill ants before growing spore producing stalks from their heads is remarkably complicated. The present work establishes the identification tools to move forward and ask how forest fragmentation affects such disease dynamics.

Hidden Diversity Behind the Zombie-Ant Fungus Ophiocordyceps unilateralis: Four New Species Described from Carpenter Ants in Minas Gerais, Brazil. (2011) PLoS ONE 6(3): e17024. doi:10.1371/journal.pone.0017024
Background: Ophiocordyceps unilateralis (Clavicipitaceae: Hypocreales) is a fungal pathogen specific to ants of the tribe Camponotini (Formicinae: Formicidae) with a pantropical distribution. This so-called zombie or brain-manipulating fungus alters the behaviour of the ant host, causing it to die in an exposed position, typically clinging onto and biting into the adaxial surface of shrub leaves. We (HCE and DPH) are currently undertaking a worldwide survey to assess the taxonomy and ecology of this highly variable species.
Methods: We formally describe and name four new species belonging to the O. unilateralis species complex collected from remnant Atlantic rainforest in the south-eastern region (Zona da Mata) of the State of Minas Gerais, Brazil. Fully illustrated descriptions of both the asexual (anamorph) and sexual (teleomorph) stages are provided for each species. The new names are registered in Index Fungorum (registration.indexfungorum.org) and have received IF numbers. This paper is also a test case for the electronic publication of new names in mycology.
Conclusions: We are only just beginning to understand the taxonomy and ecology of the Ophiocordyceps unilateralis species complex associated with carpenter ants; macroscopically characterised by a single stalk arising from the dorsal neck region of the ant host on which the anamorph occupies the terminal region and the teleomorph occurs as lateral cushions or plates. Each of the four ant species collected – Camponotus rufipes, C. balzani, C. melanoticus and C. novogranadensis – is attacked by a distinct species of Ophiocordyceps readily separated using traditional micromorphology. The new taxa are named according to their ant host.

Infectious diseases as a result of DNA virus infections are a major health concern worldwide. The major pathogenic DNA viruses include cytomegalovirus (CMV), herpes simplex virus (HSV), Epstein–Barr virus, Kaposi’s sarcoma-associated herpesvirus, polyoma virus and human papilloma virus. The two major species of herpesviruses such as CMV and HSV are clinically important. Herpes simplex virus is the cause of a wide range of diseases including some serious illnesses such as keratitis and encephalitis. Human cytomegalovirus is the major health risk in the newborn and in the immunocompromised causing congenital abnormalities and systemic diseases, respectively. Moreover, given the ability of DNA viruses to efficiently infect a wide range of cell types, these viruses also have gained clinical importance as potential gene delivery platforms to treat a variety of genetic diseases. The potent immune and inflammatory responses against the viral components however remain the stumbling block to the widespread clinical use of such vectors. Therefore a thorough mechanistic understanding of host anti-viral responses is central to the development not only of anti-viral therapeutics and vaccines but also in order to improve the safety of viral vectors in gene therapies.

Innate immune sensing of DNA viruses. Virology. Feb 17 2011
DNA viruses are a significant contributor to human morbidity and mortality. The immune system protects against viral infections through coordinated innate and adaptive immune responses. While the antigen-specific adaptive mechanisms have been extensively studied, the critical contributions of innate immunity to anti-viral defenses have only been revealed in the very recent past. Central to these anti-viral defenses is the recognition of viral pathogens by a diverse set of germ-line encoded receptors that survey nearly all cellular compartments for the presence of pathogens. In this review, we discuss the recent advances in the innate immune sensing of DNA viruses and focus on the recognition mechanisms involved.

Related:

• Toll-Like Receptors
• Virus tricks to grid-lock the type I interferon system

Background
When to initiate antiretroviral therapy in HIV infected patients is a difficult clinical decision. Actually, it is still a matter of discussion whether early highly active antiretroviral therapy (HAART) during primary HIV infection may influence the dynamics of the viral rebound, in case of therapy interruption, and overall the main disease course.
Methods
In this article we use a computational model and clinical data to identify the role of HAART timing on the residual capability to control HIV rebound after treatment suspension. Analyses of clinical data from three groups of patients initiating HAART respectively before seroconversion (very early), during the acute phase (early) and in the chronic phase (late), evidence differences arising from the very early events of the viral infection.
Results
The computational model allows a fine grain assessment of the impact of HAART timing on the disease outcome, from acute to chronic HIV-1 infection. Both patients’ data and computer simulations reveal that HAART timing may indeed affect the HIV control capability after treatment discontinuation. In particular, we find a median time to viral rebound that is significantly longer in very early than in late patients.
Conclusions
A timing threshold is identified, corresponding to approximately three weeks post-infection, after which the capability to control HIV replication is lost. Conversely, HAART initiation occurring within three weeks from the infection could allow to preserve a significant control capability. This time could be related to the global triggering of uncontrolled immune activation, affecting residual immune competence preservation and HIV reservoir establishment.

Timely HAART initiation may pave the way for a better viral control. BMC Infectious Diseases 2011, 11: 56 doi:10.1186/1471-2334-11-56

Methane produced in the biosphere is derived from two major pathways. Conversion of the methyl group of acetate to CH(4) in the aceticlastic pathway accounts for at least two-thirds, and reduction of CO(2) with electrons derived from H(2), formate, or CO accounts for approximately one-third. Although both pathways have terminal steps in common, they diverge considerably in the initial steps and energy conservation mechanisms. Steps and enzymes unique to the CO(2) reduction pathway are confined to methanogens and the domain Archaea. On the other hand, steps and enzymes unique to the aceticlastic pathway are widely distributed in the domain Bacteria, the understanding of which has contributed to a broader understanding of prokaryotic biology.

How to make a living by exhaling methane. Annu Rev Microbiol. 2010 64: 453-473

Related:

• Methane: a natural gas
• Pig Poo = Power

There are many different mechanisms of bacterial motility, by gliding motility has always been something of a mystery. It turns out that in Mycoplasma, gliding motility results from many tiny legs pedalling away like crazy. Cute, wait until the nanotech guys gets hold of this one. Oh wait, they already did.

Unique centipede mechanism of Mycoplasma gliding. Ann Rev Microbiol. (2010) 64: 519-537
Mycoplasma, a genus of pathogenic bacteria, forms a membrane protrusion at a cell pole. It binds to solid surfaces with this protrusion and then glides. The mechanism is not related to known bacterial motility systems, such as flagella or pili, or to conventional motor proteins, including myosin. We have studied the fastest species, Mycoplasma mobile, and have proposed a working model as follows. The gliding machinery is composed of four huge proteins at the base of the membrane protrusion and supported by a cytoskeletal architecture from the cell inside. Many flexible legs approximately 50 nm long are sticking out from the machinery. The movements generated by the ATP hydrolysis cell inside are transmitted to the “leg” protein through a “gear” protein, resulting in repeated binding, pull, and release of the sialylgalactose fixed on the surface by the legs. The gliding of Mycoplasma pneumoniae, a species distantly related to M. mobile, is also discussed.
Related:

• Cytoskeletal structure of Mycoplasma mobile
• Bacterial Gliding Motility: Multiple Mechanisms for Cell Movement over Surfaces. (2007) Ann. Rev. Microbiol. 55: 49-75