Autotrophic Microorganisms Research Articles

Longitudinal distributions of CO2-fixing bacteria in forest soils and their potential associations with soil multifunctionality

Autotrophic microorganisms can fix carbon dioxide (CO2) into organic carbon (C), potentially offering a natural mechanism to mitigate global climate change. Forest soils, recognized as vast and critical C repositories with significant microbial CO2 fixation rates, remain understudied, particularly regarding the spatial variations of autotrophic bacteria and their relationship to soil functions in arid regions. In this study, we systematically investigated soil multifunctionality, along with the spatial distribution of autotrophic bacterial communities identified by the RubisCO cbbL and cbbM genes, and the driving factors across a longitudinal gradient in the Loess Plateau forest soils. The investigation spanned an ∼850 km west-east transect with precipitation below 600 mm. The alpha diversity of cbbL-containing bacteria, as measured by the Chao1 index, was correlated with climatic variables such as precipitation and elevation instead of local soil characteristics. In contrast, the alpha diversity of cbbM-containing bacteria was associated with soil properties. The community composition of autotrophic bacteria, based on cbbL and cbbM genes, showed greater similarity in soils from the eastern Loess Plateau and was distinct from those in the western region. The cbbL- and cbbM-containing generalist taxa were subject to differential selection and promotion between the eastern and western regions. Temperature, soil pH and spatial variables were key drivers influencing the community composition of cbbL- and cbbM-containing bacteria. The diversity and communities of soil autotrophic bacteria significantly affected soil multifunctionality. The study demonstrates that soil autotrophic bacteria in forest soils are intricately connected to climatic conditions, soil pH and spatial factors, significantly impacting soil multifunctionality. These insights provide evidence that can be instrumental in predicting and potentially enhancing the functional capacity of forest ecosystems in the Loess Plateau.

Current regulates electron donors for heterotrophic and autotrophic microorganisms to enhance sulfate reduction in three-dimensional electrode biofilm reactors

The variability in industrial production often generates wastewater with an unstable carbon-to-sulfur ratio, challenging the concurrent removal of sulfate and organic compounds. Three-dimensional biofilm electrode reactor (3D-BER) technology offers a promising solution, compatible with both autotrophic and heterotrophic sulfate reduction. In this study, four up-flow 3D-BERs with gradient current levels were operated for nearly 400 days to treat simulated high-concentration sulfate wastewater. The effects of current intensity, hydraulic retention time (HRT), and influent carbon-to-sulfur ratio on sulfate and organic removal were investigated. The composition and functions of microbial communities were analyzed by metagenomic sequencing. The synergistic mechanism between heterotrophic and autotrophic sulfate reduction was examined by delineating their individual contributions to sulfate removal. Under optimized conditions (HRT 60 h, influent carbon-to-sulfur ratio of 1.7, and current intensity of 50 mA), the highest removal efficiencies for SO42- and COD reached 70.47 % and 85.58 %, respectively. Elevated current intensity increased the abundances of Desulfuromonadaceae, Desulfovibrionaceae and Methanobacteriaceae, while decreasing Anaerolineaceae and Geobacteraceae. Key genes involved in carbon fixation and hydrogen-relied sulfate reduction showed lower abundances at high current levels, whereas genes for direct electron uptake from the electrode were more abundant. Batch experiments demonstrated a synergistic effect between autotrophic and heterotrophic sulfate reduction, most pronounced at 50 mA. Our work successfully regulates electron donors for microbial reduction of high-concentration sulfate in 3D-BERs by manipulating current intensity, providing new insights into the application of bioelectrochemical technology for complex industrial wastewater treatment.

Electrogenic performance and carbon sequestration potential of biophotovoltaics.

Biophotovoltaics (BPV) is a clean and sustainable solar energy generation technology that operates by utilizing photosynthetic autotrophic microorganisms to capture light energy and generate electricity. However, a major challenge faced by BPV systems is the relatively low electron transfer efficiency from the photosystem to the extracellular electrode, which limits its electrical output. Additionally, the transfer mechanisms of photosynthetic microorganism metabolites in the entire system are still not fully clear. In response to this, this article briefly introduces the basic BPV principles, reviews its development history, and summarizes measures to optimize its electrogenic efficiency. Furthermore, recent studies have found that constructing photosynthetic-electrogenic microbial consortia can achieve high power density and stability in BPV systems. Therefore, the article discusses the potential application of constructing photosynthetic-electrogenic microbial aggregates in BPV systems. Since photosynthetic-electrogenic microbial communities can also exist in natural ecosystems, their potential contribution to the carbon cycle is worth further attention.

Metagenomic and isotopic insights into carbon fixation by autotrophic microorganisms in a petroleum hydrocarbon impacted red clay aquifer

Autotrophic microorganisms, the pivotal carbon fixers, exhibit a broad distribution across diverse environments, playing critical roles in the process of carbon sequestration. However, insights into their distribution characteristics in aquifers, particularly in those petroleum-hydrocarbon-contaminated (PHC) aquifers that were known for rich in heterotrophs, have been limited. In the study, groundwater samples were collected from red clay aquifers in the storage tank leakage area of a PHC site, a prevalent aquifer type in southern China and other regions. Metagenomics combined with hydrochemical and inorganic carbon isotope analyses were employed to elucidate the presence of microbial carbon fixation and its driving forces. Results showed that there were hundreds of autotrophic microorganisms participating in distinct carbon fixation processes in the red clay PHC aquifers. Reductive tricarboxylic acid (rTCA) and dicarboxylate/4-hydroxybutyrate (DC/4HB), as well as 3-hydroxypropionate (3HP or/and 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB)) were the predominant carbon fixation pathways. The abundances of carbon fixation genes and autotrophic microorganisms were significantly and positively correlated with hydrocarbon concentrations and δ13C of dissolved inorganic carbon (δ13C-DIC) values. This finding indicated that the petroleum hydrocarbon significantly promoted the proliferation of carbon fixation microorganisms, leading to a substantial uptake of inorganic carbon. Therefore, we deduce that this process holds considerable potential for carbon sequestration in PHC-contaminated aquifers.

Integration of mixotrophic denitrification and anammox in Thiothrix-hydroxyapatite coupled particles treating municipal wastewater against low temperature and organic load shocks

Sulfur-driven autotrophic denitrification coupled with anammox (SPDA) is a promising process for autotrophic nitrogen removal, but autotrophic microorganisms are challenging to retain in wastewater treatment units. In this study, a single-stage mixotrophic denitrification coupled with anammox (MDA) process was established in an up-flow anaerobic sludge bed reactor with Thiothrix-hydroxyapatite coupled particles. The advancement of the sludge granulation process effectively strengthened the resistance of the MDA system to environmental stresses, and the SPDA-dominated nitrogen removal process achieved a total nitrogen removal efficiency of 88.6 %, a nitrogen removal rate of 0.432 KgN/m3/d at temperatures as low as 12.8 °C and an organic loading rate of 0.63 KgCOD/m3/d. Interestingly, the ecological niche integration of sulfur oxidizing bacteria (SOB), anammox bacteria and heterotrophic denitrifying bacteria in the granular sludge was observed during long-term operation. The FISH-CLSM results revealed the spatial distribution of functional microorganisms in the granular sludge and the potential pollutant transformation mechanism. The aggressive growth of SOB dominated by Thiothrix constructed a biological wall at the periphery of the granules, which ensured their priority for nitrate acquisition, supplied nitrite to the internal anammox bacteria, and acted as an important barrier against the shock of organic loads. Overall, this study presents a novel granulation approach for the biological treatment of sulfur-containing wastewater, highlighting the efficacy of functional integration within Thiothrix-hydroxyapatite coupled particles as an effective strategy to resist environmental stress.

Inorganic carbon metabolism enhanced hydrogen-driven denitrification: Evaluation of carbon fixation pathways and microbial traits

H2-driven denitrification offers a promising alternative for treating low C/N wastewater amidst global nitrogen pollution, due to its advantages of high removal efficiency, low energy consumption, and independence from exogenous organic carbon source. While inorganic carbon assimilation is crucial for the growth and reproduction of autotrophic microorganisms, it remains uncertain whether the fixation of inorganic carbon could impact H2-driven denitrification. This work demonstrated that the supplement of inorganic carbon efficiently improved the efficiency of nitrate removal to 90.3%, compared to 78.0% in the control. Further analysis indicated that inorganic carbon supplementation shifted the microbial structure from autotrophic-dominated (e.g., Hydrogenophaga and Rhodococcus with abundance of 2.3% and 2.6%) to mixotrophic-dominated (e.g., Thauera and Microscillaceae sp. with abundance of 5.6% and 32.8%). Additionally, although H2 boosted the carbon fixation via the reductive TCA cycle and Wood-Ljungdahl pathway, the Calvin-Benson cycle emerged as the predominant pathway, significantly boosted under inorganic carbon supplementation, along with the upregulation of critical enzyme expression including RuBisCo (EC 4.1.1.39), PGK (EC 2.7.2.3) and GAPDH (EC 1.2.1.12). Moreover, the expressions and activities of functional enzymes involved in nitrogen transformation, including nitrate reductase (NAR), nitrite reductase (NIR) and nitric oxide reductase (NOR), as well as microbial electron transfer ability, were remarkably enhanced under sufficient inorganic carbon conditions. This work contributed to understanding the carbon metabolism mechanism in H2-driven denitrification, thereby facilitating the promotion of the efficient and low-carbon approach for nitrogen removal from wastewater.

Integrating viruses into soil food web biogeochemistry.

The soil microbiome is recognized as an essential component of healthy soils. Viruses are also diverse and abundant in soils, but their roles in soil systems remain unclear. Here we argue for the consideration of viruses in soil microbial food webs and describe the impact of viruses on soil biogeochemistry. The soil food web is an intricate series of trophic levels that span from autotrophic microorganisms to plants and animals. Each soil system encompasses contrasting and dynamic physicochemical conditions, with labyrinthine habitats composed of particles. Conditions are prone to shifts in space and time, and this variability can obstruct or facilitate interactions of microorganisms and viruses. Because viruses can infect all domains of life, they must be considered as key regulators of soil food web dynamics and biogeochemical cycling. We highlight future research avenues that will enable a more robust understanding of the roles of viruses in soil function and health.

Quorum sensing improves start-up and stability of sulfate-reducing biocathode in autotrophic microbial electrolytic cell for low-organic-carbon sulfate wastewater treatment

The utilization of autotrophic microorganisms in microbial electrolysis cell (MEC) is promising for the treatment of industrial wastewater that lacks carbon source and electron donor. However, constructing an autotrophic biocathode is time-consuming, and the population induction technologies may alleviate this challenge. In this study, N-butyryl-L-Homoserine lactone (C4-HSL) was added to the MEC biocathode run for 60 cycles to investigate quorum sensing effects on sulfate reduction efficiency, electrochemical properties, microbial community structure and functional genes. The results showed that the addition of C4-HSL significantly expedited the startup of the MEC cathode with a 47.1 % reduction. Its electrochemical performance was also improved, with the cyclic voltammetry area averaging 1.19 times higher than that without the addition of the signaling molecule. Under the regulation of C4-HSL, the biodiversity in the initiation phase became richer. The relative abundance of Desulfobacterota and sulfate reduction-related functional genes increased to 4 times and 1.43 times of the control, respectively. This discovery reveals the potential of signaling molecules in enhancing the construction of sulfate wastewater treatment reactors and improving the performance of autotrophic microorganisms, aiming to improve wastewater treatment efficiency and broaden the practical possibilities of MEC.

Hematite enhances microbial autotrophic nitrate removal in carbonate and phosphate-rich environments by increasing Fe(II) activity

Groundwater contamination by nitrates presents significant risks to both human health and the environment. In groundwater characterized as oligotrophic—low in organic carbon, but abundant in carbonate and phosphate—chemolithoautotrophic bacteria, including nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOB), play a vital role in denitrification. The chemoautotrophic nitrate reduction is sensitive to environmental factors, including widespread iron oxides like hematite in nature. However, the specific mechanisms of this influence remain unclear. We examined the mechanism of how hematite impacts autotrophic nitrate reduction in a model NRFeOB community known as culture KS. We found that hematite enhances the rate of autotrophic nitrate reduction by promoting Fe(II) oxidation. Mössbauer spectroscopy detected a significant amount of adsorbed Fe(II) when hematite was present, leading to a reduction in dissolved ferrous iron. In conjunction with XRD data, it can be inferred that the formation of vivianite decreased, thereby increasing the Fe(II) activity in the reaction system. Within the culture KS bacterial consortium, hematite fosters the proliferation of autotrophic microorganisms, specifically Gallionellaceae, and amplifies the presence of denitrifying microbes, notably Rhodanobacter. This dual enhancement improves Fe(II) utilization and nitrate reduction capabilities. Our findings highlight intricate interactions between hematite and a model NRFeOB community, offering insights into groundwater nitrate removal mechanisms and the ecological strategies of autotrophic bacteria in mineral-rich environments.

Picocyanobacterial-bacterial interactions sustain cyanobacterial blooms in nutrient-limited aquatic environments

Cyanobacterial blooms (CBs) and concomitant water quality issues in oligotrophic/mesotrophic waters have been recently reported, challenging the conventional understanding that CBs are primarily caused by eutrophication. To elucidate the underlying mechanism of CBs in nutrition-deficient waters, the changes in Chlorophyll a (Chl-a), cyanobacterial-bacterial community composition, and certain microbial function in Qingcaosha Reservoir, the global largest tidal estuary storage reservoir, were analyzed systematically and comprehensively after its pilot run (2011–2019) in this study. Although the water quality was improved and stabilized, more frequent occurrences of bloom level of Chl-a (>20 μg L−1) in warm seasons were observed during recent years. The meteorological changes (CO2, sunshine duration, radiation, precipitation, evaporation, and relative humidity), water quality variations (pH, total organic carbon content, dissolved oxygen, and turbidity), accumulated sediments as an endogenous source, as well as unique estuarine conditions collectively facilitated picocyanobacterial-bacterial coexistence and community functional changes in this reservoir. A stable and tight co-occurrence pattern was established between dominant cyanobacteria (Synechococcus, Cyanobium, Planktothrix, Chroococcidiopsis, and Prochlorothrix) and certain heterotrophic bacteria (Proteobacteria, Actinobacteria, and Bacteroidetes), which contributed to the remineralization of organic matter for cyanobacteria utilization. The relative abundance of chemoorganoheterotrophs and bacteria related to nitrogen transformation (Paracoccus, Rhodoplanes, Nitrosomonas, and Zoogloea) increased, promoting the emergence of CBs in nutrient-limited conditions through enhanced nutrient recycling. In environments with limited nutrients, the interaction between photosynthetic autotrophic microorganisms and heterotrophic bacteria appears to be non-competitive. Instead, they adopt complementary roles within their ecological niche over long-term succession, mutually benefiting from this association. This long-term study confirmed that enhanced nutrient cycling, facilitated by cyanobacterial-bacterial symbiosis following long-term succession, could promote CBs in oligotrophic aquatic environments devoid of external nutrient inputs. This study advances understanding of the mechanisms that trigger and sustain CBs under nutritional constraints, contributing to developing more effective mitigation strategies, ensuring water safety, and maintaining ecological balance.

Effects of returning peach branch waste to fields on soil carbon cycle mediated by soil microbial communities.

In recent years, the rise in greenhouse gas emissions from agriculture has worsened climate change. Efficiently utilizing agricultural waste can significantly mitigate these effects. This study investigated the ecological benefits of returning peach branch waste to fields (RPBF) through three innovative strategies: (1) application of peach branch organic fertilizer (OF), (2) mushroom cultivation using peach branches as a substrate (MC), and (3) surface mulching with peach branches (SM). Conducted within a peach orchard ecosystem, our research aimed to assess these resource utilization strategies' effects on soil properties, microbial community, and carbon cycle, thereby contributing to sustainable agricultural practices. Our findings indicated that all RPBF treatments enhance soil nutrient content, enriching beneficial microorganisms, such as Humicola, Rhizobiales, and Bacillus. Moreover, soil AP and AK were observed to regulate the soil carbon cycle by altering the compositions and functions of microbial communities. Notably, OF and MC treatments were found to boost autotrophic microorganism abundance, thereby augmenting the potential for soil carbon sequestration and emission reduction. Interestingly, in peach orchard soil, fungal communities were found to contribute more greatly to SOC content than bacterial communities. However, SM treatment resulted in an increase in the presence of bacterial communities, thereby enhancing carbon emissions. Overall, this study illustrated the fundamental pathways by which RPBF treatment affects the soil carbon cycle, providing novel insights into the rational resource utilization of peach branch waste and the advancement of ecological agriculture.

Interference of microplastics on autotrophic microbiome in paddy soils: Shifts in carbon fixation rate, structure, abundance, co-occurrence, and assembly process

Autotrophic microorganisms play a crucial role in soil CO2 assimilation. Although microplastic pollution is recognized as a significant global concern, its precise impact on carbon sequestration by autotrophic microorganisms in agroecosystem soil remains poorly understood. This study conducted microcosm experiments to explore how conventional polystyrene (PS) and biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microplastics affect carbon fixation rates (CFRs) and the community characteristics of soil autotrophic microorganisms in paddy agroecosystems. The results showed that compared with the control groups, 0.5 % and 1 % microplastic treatments significantly reduced soil CFRs by 11.8 − 24.5 % and 18.7 − 32.3 %, respectively. PS microplastics exerted a stronger inhibition effect on CFRs than PHBV microplastics in bulk soil. However, no significant difference was observed in the inhibition of CFRs by both types of microplastics in rhizosphere soils. Additionally, PS and PHBV microplastics altered the structure of autotrophic microbial communities, resulting in more stochastically dominated assembly and looser, more fragile coexistence networks compared to control groups. Moreover, microplastics drove the changes in autotrophic microbial carbon fixation primarily through their direct interference and the indirect effect by increasing soil organic carbon levels. Our findings enhance the understanding and predictive capabilities regarding the impacts of microplastic pollution on carbon sinks in agricultural soils.

Long-term subsoiling and tillage rotation increase carbon storage in soil aggregates and the abundance of autotrophs

Autotrophic microorganisms in soil can increase soil carbon (C) sequestration by utilising chemical energy released from inorganic compounds to fix atmospheric CO2. Therefore, the effects of tillage systems on soil C stocks and autotrophic microbial community deserves in-depth study. The effects of five tillage systems, including no tillage (NoTill), subsoiling (SubS), rotary tillage (RotTill, local general tillage), no tillage-subsoiling-no tillage (NoTill-SubS), and rotary tillage-subsoiling-rotary tillage (RotTill-SubS) were investigated within a 17-year field experiment. Their effects on soil aggregates, C content and enzyme activities were studied, and the impacts on C-fixing microbial communities were analysed using the C-fixing gene cbbL. The macroaggregate portion and RubisCO and ATPase activities were the highest under SubS, causing the aggregate-associated organic C (AOC) to be 93 % higher than that under RotTill. Under RotTill-SubS, SOC, AOC and aggregate-associated microbial biomass C (AMBC) were larger than those under RotTill. RotTill-SubS reduced the microaggregate portion, increased enzyme activities and the relative abundance of C-fixing bacteria, including Sphingomonadales, Burkholderiales, and Nitrosomonadales. The macroaggregate portion under NoTill-SubS and the relative abundance of Sphingomonadales and Burkholderiales was the highest. Correspondingly, the SOC content was the largest (29 % higher than that in RotTill), and the AOC and AMBC contents were 42 % and 31 % larger, respectively, than those in RotTill. Structural equation modelling reveals that increasing tillage or lowering AOC content can directly increase differences in autotrophic bacterial communities. The reduced aggregate stability decreases C content and increases ATPase and RubisCO activities can indirectly increase differences in bacterial community composition.

Controlling organic carbon increase in oxygenated marine sediment by using decarburization slag

The chemical oxygen demand (COD) in the Seto Inland Sea, Japan has increased in the recent decades due to the increase of bottom dissolved oxygen (DO) concentration which stimulated several autotrophic microorganisms, specially sulfur oxidizing bacteria (SOB). This increased SOB activity due to the oxygenation of the bottom sediment synthesized new organic matter (OM) which contributed dissolved organic carbon to the overlying seawater. This phenomenon further led to hypoxia in some subareas in the Seto Inland Sea. Higher pH or alkaline environment has been found to be an unfavorable condition for SOB. In this research, we used decarburization slag to elevate the pH of sediment to control the SOB activity and consequently reduce OM production in the sediment. Ignition loss of the surface sediment increased from 5.14% 6.38% after 21 days of incubation with aeration; whereas the sediment showed the less ignition loss of 5.71% after 21 days when the slag was incubated in the same experimental setup. Microbial community analysis showed less SOB activity in the slag added aerated sediment which accounts for the controlled increase of OM in the sediment. An additional experiment was conducted with magnesium oxide to confirm whether elevated pH can control the OM increase in sediment due to rising DO. All these results showed that decarburization slag can elevate the pH of the sediment to a certain level which can control the SOB activity followed by controlled increase of OM in the sediment. The findings may be beneficial to control accumulation of sedimentary OM which can act as a source of organic carbon in the overlying seawater.

Autotrophic degradation of sulfamethoxazole using sulfate-reducing biocathode in microbial photo-electrolysis system

Sulfamethoxazole is a representative of sulfonamide antibiotic pollutants. This study aims to investigate the degradation pathways of sulfamethoxazole and the response of microbial communities using the autotrophic biocathode in microbial photo-electrolysis systems (MPESs). Sulfamethoxazole with an initial concentration of 2 mg L−1 was degraded into small molecule propanol within 6 h with the biocathode. Elemental sulfur (S0) was detected in the cathode chamber, accounting for 57 % of the removed sulfate. The conversion from sulfate to S0 indicated that autotrophic microorganisms might adopt a novel pathway for sulfamethoxazole removal in the MPES. In the abiotic cathode, sulfamethoxazole degradation rate was 0.09 mg L−1 h−1 with the electrochemistry process. However, sulfamethoxazole was converted to products that still contain benzene rings, including p-aminothiophenol, 3-amino-5-methylisoxazole, and sulfonamide. The microbial community analysis indicated that the synergistic interaction of Desulfovibrio and Acetobacterium promoted the autotrophic degradation of sulfamethoxazole. The results suggested that autotrophic microorganisms may play an important role in the environmental transformation of sulfamethoxazole.

Novel electrochemical strategies for the microbial conversion of CO2 into biomass and volatile fatty acids using a fluid-like bed electrode in a three-phase reactor.

Microbial electrosynthesis (MES) constitutes a bioelectrochemical process where bacteria uptake electrons extracellularly from a polarized electrode to incorporate them into their anabolic metabolism. However, the efficiency of current MES reactor designs can be lower than expected due to limitations regarding electron transfer and mass transport. One of the most promising bioreactor configurations to overcome these bottlenecks is the Microbial Electrochemical Fluidized Bed Reactor (ME-FBR). In this study, microbial CO2 fixation is investigated for the first time in a ME-FBR operated as a 3-phase reactor (solid-liquid-gas). An electroconductive carbon bed, acting as a working electrode, was fluidized with gas and polarized at different potentials (-0.6, -0.8 and -1 V vs. Ag/AgCl) so it could act as an electron donor (biocathode). Under these potentials, CO2 fixation and electron transfer were evaluated. Autotrophic electroactive microorganisms from anaerobic wastewater were enriched in a ME-FBR in the presence of 2-bromoethanosulfonic acid (BES) to inhibit the growth of methanogens. Cyclic voltammetry analysis revealed interaction between the microorganisms and the cathode. Furthermore, volatile fatty acids like propionate, formate and acetate were detected in the culture supernatant. Acetate production had a maximum rate of ca. 1 g L-1 day-1 . Planktonic cell biomass was produced under continuous culture at values as high as ca. 0.7 g L-1 dry weight. Overall, this study demonstrates the feasibility of employing a fluidized electrode with gaseous substrates and electricity as the energy source for generating biomass and carboxylic acids.

Diversity of Carotenoid Pigmented Marine Photosynthetic Bacteria in the Dumai Sea Waters

Marine photosynthetic bacteria represent autotrophic microorganisms capable of synthesizing natural pigments. This study aims to explore the diversity of carotenoid-pigmented marine photosynthetic bacteria in the Dumai Sea waters, Riau Province, Indonesia. The research method was a survey using marine surface water as samples from six locations. The research was conducted in four primary phases: 1) measurement of environmental conditions; 2) enrichment and isolation of marine photosynthetic bacteria; 3) enumeration of total bacteria; and 4) analysis of pigments colour production. Isolation results and population density measurements of photosynthetic bacteria revealed fascinating patterns. The highest cell count was observed at fish auctions (sampling site 2), while the lowest cell count was recorded near a river estuary (sampling site 6). Detailed characterization studies identified ten isolates capable of producing natural carotenoid pigments exhibiting colours ranging from pink to deep red. These findings contribute to the understanding of marine microbial diversity and the potential of bacteria for biotechnology products, aquaculture, and medical applications.

Importance and profits of photo autotrophic microorganisms in composting techniques

Importance and profits of photo autotrophic microorganisms in composting techniques

Biogeographic distribution of autotrophic bacteria was more affected by precipitation than by soil properties in an arid area.

Autotrophic bacteria play an important role in carbon dioxide fixation and are widespread in terrestrial ecosystems. However, the biogeographic patterns of autotrophic bacteria and the driving factors still remain poorly understood. Herein, we conducted a 391-km north to south transect (mean annual precipitation <600 mm) survey in the Loess Plateau of China, to investigate the biogeographic distributions of autotrophic bacteria (RubisCO cbbL and cbbM genes) and the environmental drivers across different latitude sites with clear vegetational and climatic gradients. The soils in northern region with lower precipitation are dominated by grassland/forest, which is typically separated from the soils in southern region with higher precipitation. The community structure of autotrophic bacterial cbbL and cbbM genes generally differed between the soils in the southern and northern Loess Plateau, suggesting that precipitation and its related land use practices/ecosystem types, rather than local soil properties, are more important in shaping the soil autotrophic microorganisms. The cbbL-containing generalist OTUs were almost equally abundant across the northern and southern Loess Plateau, while the cbbM-containing bacterial taxa were more prevalent in the low precipitation northern region. Such differences indicate differentiate distribution patterns of cbbM- and cbbL-containing bacteria across the north to south transect. Our results suggest that the community composition and the differentiate distributions of soil cbbL- and cbbM-containing bacterial communities depend on precipitation and the related ecosystem types in the north to south transect in the Loess Plateau of China.

Spatial–temporal distribution characteristics and traceability analysis of organic matter in Shahe Reservoir (Beijing, China)

Shahe Reservoir is a key node in the upstream of the North Canal, and the water quality has gradually improved after the implementation of low water operation in 2018. The organic matter(OM) in the sediment decreased from 16.66 to 14.22%.In this study, the FI index and parallel factor method were used to investigate the traceability of OM and dissolved organic matter (DOM) in the Shahe Reservoir before and during low water level operation(LWLO), and the results showed that the terrestrial source fraction of OM in sediments was mainly related to organic-rich terrestrial plant residues carried by tributaries and overflows/outfalls during the rainy season, and the FI index indicated that the organic matter (OM) in the Shahe Reservoir before and during LWLO in each DOM in the area is derived from authigenic sources of autotrophic microorganisms, algae, etc. The parallel factor method shows that more than most of the pollutants in the DOM are input from endogenous sources and a small proportion of pollutants are input from exogenous sources. Nutrients in both sediment and interstitial water increased during the LWLO, with TN and TP levels increasing by 262.38 and 204.45 mg·kg−1 in sediment, NH4+–N, PO43−−P, TN and TP in interstitial water increasing by 0.98, 1.36, 2.07 and 4.33 mg·L−1, respectively. Pearson correlation analysis and principal component analysis showed that OM was significantly correlated with nutrients: OM and TN (p < 0.01) and OM and TP (p < 0.05) in the pre-LWLO; OM and TN and TP (p < 0.01) in the LWLO.The results suggested that organic matter pollution control should be mainly carried out from the perspective of endogenous input, focusing on controlling the release of nutrients in sediments.