Stimulation Of Microbes Research Articles

Study Investigates Conversion of Biomethane From CO2 and Biohydrogen

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 22744, “Accelerated Methanogenesis for the Conversion of Biomethane From Carbon Dioxide and Biohydrogen at Hyperthermophilic Conditions,” by Ivy C.C. Hsia, Petronas, and Mohd F.A. Wahab and Nur K.A. Jalil, Universiti Teknologi Malaysia, et al. The paper has not been peer reviewed. Copyright 2023 International Petroleum Technology Conference. Reproduced by permission. _ Methanogenesis is the conversion of CO2 to methane (CH4) using microbes. In the context of CO2 usage, the process of methanogenesis using native microbes from a particular reservoir can be a very slow process without any external intervention. The study detailed in this complete paper investigates the use of agriculture byproducts such as palm oil mill effluent (POME) as substrates, along with potential microbial isolates that can produce biohydrogen at high temperatures. The authors write that stimulation of microbes using POME as substrate with hydrogen (H2)/CO2 supplementation is important in accelerating the rate and yield of CH4 production. Introduction The authors write that a population of microbes isolated from sludge of agriculture wastes, when given proper conditions and nutrients, was able to accelerate the rate of methanogenesis. POME is an agricultural byproduct from which a huge microbial community can be manipulated for methanogenesis, specifically for hydrogen production. This study incorporates the process of dark fermentation, using POME to generate hydrogen required to convert CO2 to CH4 in a syntrophic reaction at hyperthermophilic temperatures. Accounting for both the high reservoir temperatures (above 100°C) common to Malaysia and the temperature-tolerance limit of most microorganisms in general, the authors selected 70°C as the temperature to be studied. They write that, as their team studied a range of different temperatures, anaerobic microbes showed no production of biohydrogen and CH4 above 70°C.

Physical disturbance creates bacterial dominance of benthic biological communities in tropical deltaic environments of the Gulf of Papua

Unlike many reactive continental shelf mud deposits in temperate regions, bacteria and microfauna rather than macrofauna typically dominate benthic biomass and activities over large areas of the Gulf of Papua (GoP) deltaic complex, Papua New Guinea. During mid NW monsoon periods (Jan–Feb), macrofaunal densities at Gulf stations were relatively low (260-1270m-2), large macroinfauna were absent (upper ∼25cm), and small (<0.5mm), surface deposit-feeding polychaetes and tubiculous amphipods were dominant, reflecting a frequently destabilized seabed and high sedimentation/erosion rates. Although frequent physical disturbance generally inhibits development of macrobenthic communities, some regions of the Gulf deposits are periodically colonized and extensively bioturbated during quiescent periods, as shown by preserved biogenic sedimentary structures. Bacterial inventories integrated over the top 20cm were extremely variable within each sub region of the clinoform complex. A possible bimodal pattern with bathymetric depth and distance offshore may occur: lowest-inventories within the sandy, proximal Fly River delta, an open Gulf inner topset zone (∼10–20m) having sites of relatively high inventories, an open Gulf mid-topset region with intermediate values and less extreme variation, and the outer topset—upper foreset zone (∼40–50m) where highest values are attained (7.6×1011cellscm-2). Various measures of microbial activity, including measures proportional to the cellular rRNA content and the proportion of dividing cells, indicate extremely productive populations over the upper 1-m of the seabed throughout the Gulf of Papua region. Bacterial biomass (0–20cm) including data of Alongi et al. (1991, 1992, 1995) varied from a low of 1.6±0.3gCm-2 in intertidal mud banks to a high of 190±38gCm-2 in the topset—foreset zone. Macrofaunal biomass did not exceed 2gCm-2 in any sampled region, ranging from 0.009±0 to 1.1±0.08gCm-2 with no obvious correlation with bathymetric depth (1–63m). Meiofaunal biomass was generally an order of magnitude lower than macrofaunal biomass. Relatively elevated bacterial biomass and high turnover rates are consistent with high measured rates of benthic remineralization, presumably reflecting the rapid response time of bacteria to physical reworking, the associated entrainment of organic substrate, and flushing of metabolites. Solute exchange is also enhanced below the directly mixed surface region, possibly producing ‘far field’ stimulation of microbes in underlying deposits. Physical reworking and reoxidation of sediments between ∼10 and 50m water depth maintain suboxic, nonsulfidic conditions in the upper ∼0.5–1m despite active microbial communities and high benthic remineralization rates.

Importance of rhizodeposition in the coupling of plant and microbial productivity

SummaryPlant roots influence the biological, chemical and physical properties of rhizosphere soil. These effects are a consequence of their growth, their activity and the exudation of organic compounds from them. In natural ecosystems, the linkages between inputs of carbon from plants and microbial activity driven by these inputs are central to our understanding of nutrient cycling in soil and the productivity of these systems. This coupling of plant and microbial productivity is also of increasing importance in agriculture, where the shift towards low‐input systems increases the dependence of plant production on nutrient cycling, as opposed to fertilizers. This review considers the processes by which plants can influence the cycling of nutrients in soil, and in particular the importance of organic inputs from roots in driving microbially mediated transformations of N. This coupling of plant inputs to the functioning of the microbial community is beneficial for acquisition of N by plants, particularly in low‐input systems. This occurs through stimulation of microbes that produce exoenzymes that degrade organic matter, and by promoting cycling of N immobilized in the microbial biomass via predation by protozoa. Also, plants increase the cycling of N by changes in exudation in response to nitrogen supply around roots, and in response to browsing by herbivores. Plants can release compounds in exudates that directly affect the expression of genes in microbes, and this may be an important way of controlling their function to the benefit of the plant.