Strategies to Mitigate Enteric Methane Emissions from Ruminant Animals.

Human activities account for approximately two-thirds of global methane emissions, wherein the livestock sector is the single massive methane emitter. Methane is a potent greenhouse gas of over 21 times the warming effect of carbon dioxide. In the rumen, methanogens produce methane as a by-product of anaerobic fermentation. Methane released from ruminants is considered as a loss of feed energy that could otherwise be used for productivity. Economic progress and growing population will inflate meat and milk product demands, causing elevated methane emissions from this sector. In this review, diverse approaches from feed manipulation to the supplementation of organic and inorganic feed additives and direct-fed microbial in mitigating enteric methane emissions from ruminant livestock are summarized. These approaches directly or indirectly alter the rumen microbial structure thereby reducing rumen methanogenesis. Though many inorganic feed additives have remarkably reduced methane emissions from ruminants, their usage as feed additives remains unappealing because of health and safety concerns. Hence, feed additives sourced from biological materials such as direct-fed microbials have emerged as a promising technique in mitigating enteric methane emissions.

Self-assembly of MPG1, a hydrophobin protein from the rice blast fungus that forms functional amyloid coatings, occurs by a surface-driven mechanism.

Rice blast is a devastating disease of rice caused by the fungus Magnaporthe oryzae and can result in loss of a third of the annual global rice harvest. Two hydrophobin proteins, MPG1 and MHP1, are highly expressed during rice blast infections. These hydrophobins have been suggested to facilitate fungal spore adhesion and to direct the action of the enzyme cutinase 2, resulting in penetration of the plant host. Therefore a mechanistic understanding of the self-assembly properties of these hydrophobins and their interaction with cutinase 2 is crucial for the development of novel antifungals. Here we report details of a study of the structure, assembly and interactions of these proteins. We demonstrate that, in vitro, MPG1 assembles spontaneously into amyloid structures while MHP1 forms a non-fibrillar film. The assembly of MPG1 only occurs at a hydrophobic:hydrophilic interface and can be modulated by MHP1 and other factors. We further show that MPG1 assemblies can much more effectively retain cutinase 2 activity on a surface after co-incubation and extensive washing compared with other protein coatings. The assembly and interactions of MPG1 and MHP1 at hydrophobic surfaces thereby provide the basis for a possible mechanism by which the fungus can develop appropriately at the infection interface.

Domain-swap polymerization drives the self-assembly of the bacterial flagellar motor.

Large protein complexes assemble spontaneously, yet their subunits do not prematurely form unwanted aggregates. This paradox is epitomized in the bacterial flagellar motor, a sophisticated rotary motor and sensory switch consisting of hundreds of subunits. Here we demonstrate that Escherichia coli FliG, one of the earliest-assembling flagellar motor proteins, forms ordered ring structures via domain-swap polymerization, which in other proteins has been associated with uncontrolled and deleterious protein aggregation. Solution structural data, in combination with in vivo biochemical cross-linking experiments and evolutionary covariance analysis, revealed that FliG exists predominantly as a monomer in solution but only as domain-swapped polymers in assembled flagellar motors. We propose a general structural and thermodynamic model for self-assembly, in which a structural template controls assembly and shapes polymer formation into rings.

Backbone and sidechain (1)H, (13)C and (15)N chemical shift assignments of the hydrophobin MPG1 from the rice blast fungus Magnaporthe oryzae.

Fungal hydrophobins are secreted proteins that self-assemble at hydrophobic:hydrophilic interfaces. They are essential for a variety of processes in the fungal life cycle, including mediating interactions with surfaces and infection of hosts. The fungus Magnaporthe oryzae, the causative agent of rice blast, relies on the unique properties of hydrophobins to infect cultivated rice as well as over 50 different grass species. The hydrophobin MPG1 is highly expressed during rice blast pathogenesis and has been implicated during host infection. Here we report the backbone and sidechain assignments for the class I hydrophobin MPG1 from the rice blast fungus Magnaporthe oryzae.

Surface functionalization of carbon nanomaterials by self-assembling hydrophobin proteins.

Class I fungal hydrophobins are small surface-active proteins that self-assemble to form amphipathic monolayers composed of amyloid-like rodlets. The monolayers are extremely robust and can adsorb onto both hydrophobic and hydrophilic surfaces to reverse their wettability. This adherence is particularly strong for hydrophobic materials. In this report, we show that the class I hydrophobins EAS and HYD3 can self-assemble to form a single-molecule thick coating on a range of nanomaterials, including single-walled carbon nanotubes (SWCNTs), graphene sheets, highly oriented pyrolytic graphite, and mica. Moreover, coating by class I hydrophobin results in a stable, dispersed preparation of SWCNTs in aqueous solutions. No cytotoxicity is detected when hydrophobin or hydrophobin-coated SWCNTs are incubated with Caco-2 cells in vitro. In addition, we are able to specifically introduce covalently linked chemical moieties to the hydrophilic side of the rodlet monolayer. Hence, class I hydrophobins provide a simple and effective strategy for controlling the surfaces of a range of materials at a molecular level and exhibit strong potential for biomedical applications.