Patterns of extracellular enzyme activities among pelagic marine microbial communities: implications for cycling of dissolved organic carbon

ABSTRACT Free-living and surface-associated microbial communities in sand-packed columns perfused with groundwater were compared by examination of compositional and functional characteristics. The composition of the microbial communities was assessed by bulk DNA extraction, PCR amplification of 16S ribosomal DNA fragments, separation of these fragments by denaturing gradient gel electrophoresis, and sequence analysis. Community function was assessed by measurement of β-glucosidase and aminopeptidase extracellular enzyme activities. Free-living populations in the aqueous phase exhibited a greater diversity of phylotypes than populations associated with the solid phase. The attached bacterial community displayed significantly greater β-glucosidase and aminopeptidase enzyme activities per volume of porous medium than those of the free-living community. On a per-cell basis, the attached community had a significantly higher cell-specific aminopeptidase enzyme activity (1.07 × 10−7 nmol cell−1 h−1) than the free-living community (5.02 × 10−8 nmol cell−1 h−1). Conversely, the free-living community had a significantly higher cell-specific β-glucosidase activity (1.92 × 10−6 nmol cell−1 h−1) than the surface-associated community (6.08 × 10−7 nmol cell−1 h−1). The compositional and functional differences observed between these two communities may reflect different roles for these distinct but interacting communities in the decomposition of natural organic matter or biodegradation of xenobiotics in aquifers.

Download Full-text

Distribution of soil nutrients, extracellular enzyme activities and microbial communities across particle-size fractions in a long-term fertilizer experiment

Applied Soil Ecology ◽

10.1016/j.apsoil.2015.05.005 ◽

2015 ◽

Vol 94 ◽

pp. 59-71 ◽

Cited By ~ 55

Author(s):

Qian Zhang ◽

Wei Zhou ◽

Guoqing Liang ◽

Jingwen Sun ◽

Xiubin Wang ◽

...

Keyword(s):

Particle Size ◽

Microbial Communities ◽

Soil Nutrients ◽

Enzyme Activities ◽

Extracellular Enzyme ◽

Size Fractions ◽

Particle Size Fractions ◽

Extracellular Enzyme Activities ◽

Fertilizer Experiment

Download Full-text

Effects of tree species and N additions on forest floor microbial communities and extracellular enzyme activities

Soil Biology and Biochemistry ◽

10.1016/j.soilbio.2010.08.012 ◽

2010 ◽

Vol 42 (12) ◽

pp. 2161-2173 ◽

Cited By ~ 109

Author(s):

Matthew P. Weand ◽

Mary A. Arthur ◽

Gary M. Lovett ◽

Rebecca L. McCulley ◽

Kathleen C. Weathers

Keyword(s):

Microbial Communities ◽

Tree Species ◽

Enzyme Activities ◽

Forest Floor ◽

Extracellular Enzyme ◽

Extracellular Enzyme Activities ◽

N Additions

Download Full-text

Patterns of extracellular enzyme activities and microbial metabolism in an Arctic fjord of Svalbard and in the northern Gulf of Mexico: contrasts in carbon processing by pelagic microbial communities

Frontiers in Microbiology ◽

10.3389/fmicb.2013.00318 ◽

2013 ◽

Vol 4 ◽

Cited By ~ 13

Author(s):

Carol Arnosti ◽

Andrew D. Steen

Keyword(s):

Gulf Of Mexico ◽

Microbial Communities ◽

Enzyme Activities ◽

Extracellular Enzyme ◽

Microbial Metabolism ◽

Extracellular Enzyme Activities ◽

Northern Gulf Of Mexico ◽

Arctic Fjord ◽

Carbon Processing

Download Full-text

Understory vegetation plays a key role in sustaining soil microbial biomass and extracellular enzyme activities

10.5194/bg-2017-545 ◽

2018 ◽

Author(s):

Yang Yang ◽

Xinyu Zhang ◽

Jifu Wang ◽

Chuang Zhang ◽

Huimin Wang ◽

...

Keyword(s):

Microbial Biomass ◽

Organic Carbon ◽

Enzyme Activities ◽

Extracellular Enzyme ◽

Chinese Fir ◽

Understory Vegetation ◽

Extracellular Enzyme Activities ◽

Soil Microbial ◽

Vegetation Removal ◽

Soil Environmental Factors

Abstract. It is desirable to learn more how understory vegetation affects soil microbial biomass and extracellular enzyme activities in a subtropical Chinese fir (Cunninghamia lanceolata) forests. The aim of this study was to determine the role of understory vegetation in controlling soil properties, through an examination of the effects of understory vegetation on soil environmental factors, microbial biomass, and extracellular enzyme activities. One paired treatment, which comprised understory vegetation removal (None) and understory vegetation left intact (Understory) in the context of litter removal, was established in a subtropical Chinese fir plantation. We mainly evaluated the effects of understory vegetation on soil environmental factors, the biomass of bacteria, fungi and actinomycetes, and the activities of five hydrolases, i.e., α-1,4-glucosidase, β-1,4-glucosidase (βG), β-1,4-N-acetylglucosaminidase (NAG), β-1,4-xylosidase and acid phosphatase (AP), and two oxidase, i.e., phenol oxidase (PPO) and peroxidase (PER). The soil moisture content (SMC), and the concentrations of soil dissolved organic carbon (DOC), particulate organic carbon (POC), soil organic carbon (SOC), ammonia nitrogen (NH4+-N), and total nitrogen, and the POC / SOC ratio declined by 4 % to 34 %, and the biomass of soil bacteria and fungi, total PLFA contents, and the activities of βG, NAG, PPO, and PER were between 13 % and 27 % lower, when understory vegetation was removed. The highest activity of AP among all the measured enzymes may reflect the P was limited in this area, while NAG was positive with the concentration of NO3−-N, reflected that P- and N-degrading enzyme affected by different mechanism. The positive relationship between DOC and AP implied that microorganisms absorb carbon to meet their needs for phosphorus. The concentrations of NO3−-N and NH4+-N were positively correlated with and αG and βG suggested the increased availability of N promoted the decomposition of carbon. Understory vegetation removal inhibited the propagation of microorganisms and restricted their enzyme activities, by reducing soil energy and above-ground nutrient inputs and altering the soil micro-environment. We therefore propose that, to sustain soil quality in subtropical Chinese fir plantations, understory vegetation should be maintained.

Download Full-text

Plant and Soil Enzyme Activities Regulate CO2 Efflux in Alpine Peatlands After 5 Years of Simulated Extreme Drought

Frontiers in Plant Science ◽

10.3389/fpls.2021.756956 ◽

2021 ◽

Vol 12 ◽

Author(s):

Zhongqing Yan ◽

Enze Kang ◽

Kerou Zhang ◽

Yong Li ◽

Yanbin Hao ◽

...

Keyword(s):

Organic Carbon ◽

Plant Growth ◽

Polyphenol Oxidase ◽

Enzyme Activities ◽

Extracellular Enzyme ◽

Extreme Drought ◽

Impact Factors ◽

Extracellular Enzyme Activities ◽

Standing Biomass ◽

Plant Coverage

Increasing attention has been given to the impact of extreme drought stress on ecosystem ecological processes. Ecosystem respiration (Re) and soil respiration (Rs) play a significant role in the regulation of the carbon (C) balance because they are two of the largest terrestrial C fluxes in the atmosphere. However, the responses of Re and Rs to extreme drought in alpine regions are still unclear, particularly with respect to the driver mechanism in plant and soil extracellular enzyme activities. In this study, we imposed three periods of extreme drought events based on field experiments on an alpine peatland: (1) early drought, in which the early stage of plant growth occurred from June 18 to July 20; (2) midterm drought, in which the peak growth period occurred from July 20 to August 23; and (3) late drought, in which the wilting period of plants occurred from August 23 to September 25. After 5 years of continuous extreme drought events, Re exhibited a consistent decreasing trend under the three periods of extreme drought, while Rs exhibited a non-significant decreasing trend in the early and midterm drought but increased significantly by 58.48% (p < 0.05) during the late drought compared with the ambient control. Plant coverage significantly increased by 79.3% (p < 0.05) in the early drought, and standing biomass significantly decreased by 18.33% (p < 0.05) in the midterm drought. Alkaline phosphatase, polyphenol oxidase, and peroxidase increased significantly by 76.46, 77.66, and 109.60% (p < 0.05), respectively, under late drought. Structural equation models demonstrated that soil water content (SWC), pH, plant coverage, plant standing biomass, soil β-D-cellobiosidase, and β-1,4-N-acetyl-glucosaminidase were crucial impact factors that eventually led to a decreasing trend in Re, and SWC, pH, β-1,4-glucosidase (BG), β-1,4-xylosidase (BX), polyphenol oxidase, soil organic carbon, microbial biomass carbon, and dissolved organic carbon were crucial impact factors that resulted in changes in Rs. Our results emphasize the key roles of plant and soil extracellular enzyme activities in regulating the different responses of Re and Rs under extreme drought events occurring at different plant growth stages.

Download Full-text

Understory vegetation plays the key role in sustaining soil microbial biomass and extracellular enzyme activities

Biogeosciences ◽

10.5194/bg-15-4481-2018 ◽

2018 ◽

Vol 15 (14) ◽

pp. 4481-4494 ◽

Cited By ~ 4

Author(s):

Yang Yang ◽

Xinyu Zhang ◽

Chuang Zhang ◽

Huimin Wang ◽

Xiaoli Fu ◽

...

Keyword(s):

Microbial Biomass ◽

Organic Carbon ◽

Enzyme Activities ◽

Soil Microbial Biomass ◽

Extracellular Enzyme ◽

Chinese Fir ◽

Understory Vegetation ◽

Soil C ◽

Extracellular Enzyme Activities ◽

Soil Microbial

Abstract. While we know that understory vegetation affects the soil microbial biomass and extracellular enzyme activities in subtropical Chinese fir (Cunninghamia lanceolata) forests, we are less certain about the degree of its influence. We determined the degree to which the soil abiotic and biotic properties, such as PLFAs and extracellular enzyme activities, were controlled by understory vegetation. We established a paired treatment in a subtropical Chinese fir plantation, which comprised one plot from which the understory vegetation and litter were removed (None) and another from which the litter was removed but the understory vegetation was left intact (Understory). We evaluated how the understory vegetation influenced the soil abiotic properties, the bacterial, fungal, and actinobacterial PLFAs, and the activities of five hydrolases and two oxidative enzymes. The dissolved organic carbon (DOC), particulate organic carbon, soil organic carbon, ammonia nitrogen (NH4+–N), and total nitrogen contents and soil moisture were 18 %, 25 %, 12 %, 34 %, 8 %, and 4 % lower in the None treatments than in the Understory treatments, respectively (P<0.05). Soil bacterial, fungal, and total PLFAs, and the potential activities of β-1,4-glucosidase (βG), β-1,4-N-acetylglucosaminidase, phenol oxidase, and peroxidase, were as much as 24 % lower in None treatments than in Understory treatments (P<0.05). The specific activities of C-acquiring enzymes were as much as 41 % higher (P<0.05), and the ratio of C- to N-acquiring enzymes was also higher in the None treatments than in the Understory treatments. This suggests that in the absence of understory vegetation microbes invested more in C acquisition than N acquisition because the carbon (C) inputs were less labile. The negative relationship between DOC and AP shows that DOC is consumed when P-acquiring enzymes are produced. The positive correlation between NH4+–N and βG suggested the increased availability of N promoted the decomposition of C. More extracellular enzymes that degrade soil organic matter are produced when there is understory vegetation, which leads to losses of soil C. On the other hand, the soil C sink is maintained by increased inputs of C. We can therefore conclude that understory vegetation contributes to C sequestration in Chinese fir forests and suggest that understory should be maintained to sustain soil quality in subtropical Chinese fir plantations.

Download Full-text

Differential Organic Carbon Mineralization Responses to Soil Moisture in Three Different Soil Orders Under Mixed Forested System

Frontiers in Environmental Science ◽

10.3389/fenvs.2021.682450 ◽

2021 ◽

Vol 9 ◽

Author(s):

Shikha Singh ◽

Sindhu Jagadamma ◽

Junyi Liang ◽

Stephanie N. Kivlin ◽

Jeffrey D. Wood ◽

...

Keyword(s):

Soil Moisture ◽

Microbial Community ◽

Organic Carbon ◽

Enzyme Activities ◽

Microbial Respiration ◽

Extracellular Enzyme ◽

Water Holding Capacity ◽

Organic C ◽

Extracellular Enzyme Activities ◽

Water Holding

Soil microbial respiration is one of the largest sources of carbon (C) emissions to the atmosphere in terrestrial ecosystems, which is strongly dependent on multiple environmental variables including soil moisture. Soil moisture content is strongly dependent on soil texture, and the combined effects of texture and moisture on microbial respiration are complex and less explored. Therefore, this study examines the effects of soil moisture on the mineralization of soil organic C Soil organic carbon in three different soils, Ultisol, Alfisol and Vertisol, collected from mixed forests of Georgia, Missouri, and Texas, United States , respectively. A laboratory microcosm experiment was conducted for 90 days under different moisture regimes. Soil respiration was measured weekly, and destructive harvests were conducted at 1, 15, 60, and 90 days after incubation to determine extractable organic C (EOC), phospholipid fatty acid based microbial community, and C-acquiring hydrolytic extracellular enzyme activities (EEA). The highest cumulative respiration in Ultisol was observed at 50% water holding capacity (WHC), in Alfisol at 100% water holding capacity, and in Vertisol at 175% WHC. The trends in Extractable Organic Carbon were opposite to that of cumulative microbial respiration as the moisture levels showing the highest respiration showed the lowest EOC concentration in all soil types. Also, extracellular enzyme activities increased with increase in soil moisture in all soils, however, respiration and EEA showed a decoupled relationship in Ultisol and Alfisol soils. Soil moisture differences did not influence microbial community composition.

Download Full-text