Biology subjects

Bruns, M. A.

Publications and source records attributed to Bruns, M. A..

3 recordsLinked to original sources

bioRxiv2024

Insight into the Impact of Air Flow Rate on Algal-Bacterial Granules: Reactor Performance, Hydrodynamics by Computational Fluid Dynamics (CFD) and Microbial Community Analysis

Algal-bacterial granules have been drawing attention in wastewater treatment due to their rapid settling ability and efficient nutrient removal performance. This study evaluated the impact of air flow rates on nitrogen removal and the formation of algal-bacterial granules in domestic wastewater treatment. The highest nitrogen removal efficiency was achieved by operating with two separate feedings and the addition of an external carbon source. The higher air flow rate resulted in a higher nitrification rate and produced smaller and more compact granules on average. However, increasing the air flow rate did not necessarily increase extracellular polymeric substances (EPS) production. Computational Fluid Dynamics (CFD) simulations revealed that mechanical mixing was the primary source of shear force. Increasing the air flow rate from 0.2 LPM to 0.5 LPM only yielded a 12% increment in the volume-averaged strain rate. Further analysis of microbial communities showed that changes in bioreactor operation, especially sodium acetate addition and aerations, shifted the microbial community composition. The sodium acetate addition led to the increase of microbial diversity and the relative abundance of denitrifiers such as Thauera, while the aeration caused the increasing relative abundances of nitrogen-related genera (such as Nitrospira) and the decreasing relative abundances of cyanobacteria and Chlorella in the long-term operation of the photobioreactors. Moreover, the decrease in total abundance of grazers and pathogens along with the operation, including Chytridiomycetes, Sessilida, and Operculariidae, might result from the shear force and the decrease of prokaryotic species, such as Chlorella spp.. HighlightsO_LIA higher air flow rate resulted in a higher nitrification rate. C_LIO_LIShear stress, microbial composition, and carbon source affected EPS production. C_LIO_LIIncreasing the air flow rate from 0.2 to 0.5 LPM led to only 12% of the increment of shear stress. C_LIO_LIMicrobial community differed with aeration rate and carbon source. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=175 SRC="FIGDIR/small/589810v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@c6a7e1org.highwire.dtl.DTLVardef@37da84org.highwire.dtl.DTLVardef@eb362dorg.highwire.dtl.DTLVardef@31d122_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

Positive relationship between substrate-induced respiration rate and translationally active bacteria count in soil

Soil microorganisms carry out many processes that are fundamental to soil functions. Among the millions of microbial cells present in a gram of soil, however, less than 2% are commonly estimated to be active at any point in time. Because the respiratory response of a bulk soil to carbon substrate addition would be expected to reflect the number of active cells, we hypothesized a positive correlation between active cells and soil respiration rates during substrate-induced respiration (SIR) assays. To test this, we monitored respiration and active cell counts during 24-h incubations of agricultural soil subsamples after treating with two carbon substrates or a water-only control. We enumerated active cells with the Bioorthogonal Non-canonical Amino Acid Tagging (BONCAT) method. BONCAT provides a labeled amino acid for active cells to incorporate into newly synthesized proteins, which can then be tagged with a fluorescent dye to enable enumeration by flow cytometry. Both respiration rates and active cell counts increased over time and were positively correlated with each other after 6 h of incubation. After 24 h, increases in active cells were proportionally greater than increases in respiration. Additionally, carbon-amended soils had higher respiration rates than water-only soils with similar active cell counts, suggesting differences in carbon use efficiency. Our study documents for the first time the respiratory response from in-situ microbial activation induced by substrate amendment of soil within 6 h, a short enough timescale to exclude most cell replication. This study also demonstrates that the correlation between active cell numbers and respiration is substrate-dependent. IMPORTANCEWhile many critical ecosystem services provided by soil are known to rely on microbial activity, the soil microbial community largely remains a black box. While respiration is a common indicator of bulk soil microbial activity, this study demonstrates that the relationship between respiration and the number of active cells differs based on available carbon substrates. Advancing knowledge in this area will both enable better interpretation of biological soil tests by land managers and inform researchers modeling contributions of soil microbial respiration to global carbon dynamics.

ecology↗

bioRxiv2021

Tillage intensity and plant rhizosphere selection shape bacterial-archaeal assemblage diversity and nitrogen cycling genes

In agriculture, adoption of reduced tillage practices is a widespread adaptation to global change. The cessation of plowing reduces erosion, slows soil organic matter oxidation, and promotes soil carbon accrual, but it can also result in the development of potential N2O spots from denitrification activity. In this study, we hypothesized that 16S rRNA-based composition of bacterial-archaeal assemblages would differ in agricultural soils subjected for forty years to a range of disturbance intensities, with annual moldboard plowing (MP) being the most intensive. No-till planting (NT) represented tillage management with the least amount of disturbance, while chisel-disking (CD), a type of conservation tillage, was intermediate. All long-term tillage plots had been planted with the same crops grown in a three-year crop rotation (corn-soybean-small grain+cover crop), and both bulk and rhizosphere soils were analyzed from the corn and soybean years. We also evaluated denitrification gene markers by quantitative PCR at multiple points (three growth stages of corn and soybean). Tillage intensity, soil compartment (bulk or rhizosphere), crop year, growth stage, and interactions all exerted effects on community diversity and composition. Compared to MP and CD, NT soils had lower abundances of denitrification genes, higher abundances of nitrate ammonification genes, and higher abundances of taxa at the family level associated with the inorganic N cycle processes of archaeal nitrification and anammox. Soybean rhizospheres exerted stronger selection on community composition and diversity relative to corn rhizospheres. Interactions between crop year, management, and soil compartment had differential impacts on N gene abundances related to denitrification and nitrate ammonification. Opportunities for managing hot spots or hot moments for N losses from agricultural soils may be discernible through improved understanding of tillage intensity effects, although weather and crop type are also important factors influencing how tillage influences microbial assemblages and N use.

microbiology↗