Microbes and Climate Change Lecture 2 PDF

+ Microbes and Climate Change Lecture 2 Dr. Florence Abram + 2 Lecture Overview n Focus on: n Soil microbial communities and plant-microbe interactions n Rumen microbiome +...

+ Microbes and Climate Change Lecture 2 Dr. Florence Abram + 2 Lecture Overview n Focus on: n Soil microbial communities and plant-microbe interactions n Rumen microbiome + 3 Soil microbiome n Soil: 1 billion (109) microbial cells per gram of soil n Microbiome intrinsically linked to ecosystem functioning due to C and N cycling abilities n Verylittle known about how soil microbiome will be affected by climate change + 4 Soil microbiome n Soils are unique and highly heterogeneous n Soil microbiome stability likely to be very varied in different soils n Soil microbiome will be dependent on soil type (physicochemical characteristics), soil treatment, soil history, geographical locations… n Knowledge on what controls soil microbial community stability is crucial to predict impact of climate change on soil microbiome and associated processes + 5 Climate change n Expectedto result in increased frequency of drought and heavy rainfall n Increase in temperatures n Increase in litter inputs and plant exudates due to elevated atmospheric CO2 concentrations n Significant impact on soil microbiome + 6 Plant-microbes interactions n Presence of plants strongly increases microbiome resistance n All land plant taxa have well established symbioses with a large diversity of microorganisms n Microorganisms can support plant growth and increase plant tolerance to biotic and abiotic stress n Some colonise the rhizosphere or the root system + 7 Climate change n Climate change: altered environmental conditions likely to induce changes in plant physiology and root exudation n Increased CO2 leads to increased C allocation to the root zone and altered composition of root exudates n Increased temperature and drought likely to lead to changes in composition, abundance and activity of plant microbiota n Beneficial microorganisms might be unable to colonise plants + 8 Plant-microbes interactions n Plant growth promoting microorganisms are applied as biocontrol agents, biofertilisers and also phytostimulators in agriculture n Important to understand impact of climate change on their physiology since might alter their performance with a direct impact for agriculture n About 90% of plants form fungal associations and 60% of these establish a symbiosis with an obligate symbiont: microbe enhances plant nutrient uptake in exchange for carbohydrate source or specific environmental protection (N-fixer in nodule) + 9 Increased CO2 n Increased CO2 reported to lead to increase fungal infection some cases (Neotyphodium sp.) fungi n In produce toxins harmful to ruminants n Knock on effect on the rest of the ecosystem + 10 Increased CO2 n Specific bacteria respond differently to increased CO2 when associated with different plants n In grassland systems when elevated CO2: n Reduced level of Pseudomonas sp. , which can act as inhibitor to fungal disease + 11 Plant-microbes interactions n Pseudomonas sp increased lettuce growth under elevated CO2 n Also beneficial under drought conditions n Bacteria can be used to alleviate stresses resulting from climate change + 12 Temperature stress n Some rhizospheric bacteria have been shown to alleviate temperature stress on plants n These bacteria can be used to promote growth of different crops in different climates, soils and temperatures + 13 Increased temperature n Some strains of plant growth promoting bacteria grow better at higher temperature and could be of specific interest for agriculture exposed to increased temperatures n Rhizobia isolated from desert plants grew better at 36°C than at 26°C: tailored physiology compared to other Rhizobium sp + 14 Drought n Drought usually leads to reduced plant growth n Droughtcan significantly impact on plant microbiome n Some microorganisms can improve plant growth during drought stress exposure n2 mechanisms: n Drought avoidance (morphological adaptation) n Drought tolerance (physiological and biochemical adaptation) + 15 Drought n Neotyphodium sp and Arizona fescue under drought stress: n Higher net water assimilation rates n Production of less dense leaves n Greater leaf area per total plant biomass + 16 Climate change n Climate change will impact plant beneficial microorganisms in many ways n Effectwill depend on climate change factor, plant species, microbial species, ecosystem type and soil type n Highly complicated to study and predict + 17 Climate change n Alteration in plant beneficial microbial communities may ultimately influence plant diversity, which will in turn have huge consequences on soil microbiota n Climate change will induce adaptation processes in plant and microbes n Microorganisms likely important role to play in selecting plant that can optimally adapt to new environmental conditions imposed by climate change + Rumen microbiome 18 + 19 Agri-food industry n Irish agri-food industry: export value of over €9 bn n Employ 8% of national workforce n Irish largest indigenous sector, critical for growth and development n Ruminant-based production systems of particular interest since represents over €4 bn, 70% of gross agricultural output and 50% of export value + 20 Agri-food industry n Worldagriculture faces major challenges:70% increase in food requirements for a rapidly growing population estimated to reach 9 bn by 2050 n Increased food production must be achieved while adhering to strict environmental legislation in line with the Kyoto protocol n Fermentationin the rumen is accompanied by the production of GHG + 21 Climate change n GHG emission from ruminant production is of particular interest since mainly CH4 n Methane comprises up to 16% of GHG emissions and its warming potential is nearly 25 x greater than that of CO2 n Methane emission from agriculture represents 40% of total anthropogenic production n With enteric fermentation from ruminants representing the largest single contribution (25%) + 22 Climate change n CH4 emission from ruminants varies based on: n geographical location n feed composition n feed intake n processing of feed n animal breed n Apart from environmental issues, also accounts for up to 15% loss of ingested energy from the rumen + 23 Climate change n 87% of enteric CH4 is produced in rumen n Remainder being released from fermentation in the large intestine n Three main factors influencing rumen emissions from ruminants: n Level of feed intake n Type of carbohydrate fed n Rumen microflora n CH4 production by rumen microbiome (anaerobic digestion)  Complex organic molecules 24 (plant polysaccharides) Hydrolytic/fermentative bacteria Simpler monomers Fermentative/acidogenic bacteria Volatile fatty acids (mainly acetate propionate and butyrate) Acetogenic bacteria Acetate, CO2, H2 Methanogenic archaea Methane (CH4) + 25 Strategies to reduce ruminant CH4 emissions n Dietary changes n Microbial interventions + 26 Nutrient composition n Certain grass and shrub varieties shown to lead to significantly lower methane production in vitro n Grazing on these but will not necessarily translate in vivo (need to be investigated) + 27 Plant metabolites n Tannins and other plant secondary metabolites are toxic to protozoa, fibrolytic bacteria and methanogens n May help reduce methanogenesis n Shown to reduce methanogenesis in sheep, cows and goats but also lead to reduce food efficiency + 28 Lipid supplementation n Vegetablesand animal lipids usually used in ruminant feed to increase their energy density n Also useful to reduce methanogenesis n Estimated that fat can reduce methane emission by 4 to 5% for every 1% increase in fat content of the diet n However inclusion of lipids at levels above 6 to 7% can reduce feed intake and fibre digestibility resulting in lower milk yield or daily gain + 29 Organic acid addition n Inclusionof organic acids (fumarate, malate) in diets lead to a shift in rumen fermentation toward propionate (instead of acetate), leading to less methane production n High cost of purified organic acids makes such supplementation not economically viable n However supplementation with plant naturally rich in organic acids has some potential n More research needed + 30 Methanogenic diversity n Inorder to target methanogens, information on their population dynamics, physiology and diversity in the rumen is crucial n Methanobacteriales, Methanomicrobiales and Methanosarcinales commonly present in rumen microbiome n Recentlya novel group (named rumen Cluster C) found to be highly abundant in ruminants + 31 Phage therapy n Lytic potential of phages make them interesting for methane mitigation strategies n Phage are host specific so phage-based mitigation strategies could be developed to specifically target methanogens, however likely to have a knock-on effect on the rest of the microbiome n Phage and host typically involved in a rapid evolutionary race as host changes to avoid infection and phage changes to maintain infectivity + 32 Immunisation n Host immunisation: vaccines against methanogens n So far 3 vaccines were developed n VF3 targeting 3 methanogens n VF7 targeting 7 methanogens n One targeting 5 methanogens n The2 first vaccines could reduce 8% of methane emission despite only targeting less than 20% of methanogenic community + 33 Immunisation n Vaccine against 5 methanogens was administrated 3 times to sheep n Overall targeted 52% of methanogenic community n But led to an increase in methane production by 18% n Must have created a niche for more potent methanogens n Further research needed + 34 Microbial interventions n Animal variations in methane emissions: n Host genetics? n Diet n Lifestyle (voluntary feed intake) n Attempt to exchange rumen content from one cow to another that had same diet but divergent fermentation profiles n Both cows displayed ‘before transfer profile’ within 24 h and microbiota structure returned to ‘before transfer’ within 14 days for one cow and within 61 days for the other (resilience) + 35 Microbial interventions n Probiotics: might not persist n Needto understand how rumen microbiota forms from birth and throughout animal life n Rumen exchange promising strategy in theory even though first attempt not successful (see human and Clostridium difficile) n Mighthave to redose or develop inoculum as probiotics + 36 Conclusions n Microorganisms play a crucial role in ecosystems n Assuch will play very important role in mitigating climate change effects n Lotsof work to be done to come up with solutions need to gather relevant information (use omics)