Plant growth promoting bacteria promote rice growth cultivated in two different sandy soils subjected distinct climates conditions.

Sandy soils contain around 70% sand in their composition, making them highly fragile and susceptible to land degradation. Practices such as no-tillage cultivation, the use of bioinoculants, and the application of organic amendments can restore the organic matter in these soils, ensuring sustainable production. In this context, this work aimed to study the microbiological aspects of two sandy soil areas (Brazilian Northeast and South) under contrasting climatic conditions (tropical and temperate). With this purpose, prokaryotic communities were evaluated, and the plant growth-promoting potential of isolated bacteria was assessed by rice inoculation in sandy soil. Despite the high sand content in both soils, soil from the NE was related to the highest phosphorous, calcium, potassium, copper, sodium, zinc, magnesium, and manganese contents, organic matter percentage, and pH. The Shannon diversity index indicated that prokaryotic communities in NE were more diverse than in SU, and PCA revealed that microbial composition exhibited distinct patterns. The rice inoculation experiments were executed to verify if the bacterial isolates displayed a similar growth promotion potential when inoculated in sandy soil areas subjected to different climatic conditions. When all PGP characteristics evaluated were pooled in a PCA, a similar pattern was observed for SU and NE. Burkholderia sp. SU94 was related to highest PGP characteristics evaluated. Paraburkholderia sp. NE32 showed similar results to those of the non-inoculated control. This similar effect of rice growth in the Northeast and South of Brazil suggests that isolate SU94 adapts to different environmental conditions.

Acidophilic sulphate-reducing bacteria: Diversity, ecophysiology, and applications.

Acidophilic sulphate-reducing bacteria (aSRB) are widespread anaerobic microorganisms that perform dissimilatory sulphate reduction and have key adaptations to tolerate acidic environments (pH <5.0), such as proton impermeability and Donnan potential. This diverse prokaryotic group is of interest from physiological, ecological, and applicational viewpoints. In this review, we summarize the interactions between aSRB and other microbial guilds, such as syntrophy, and their roles in the biogeochemical cycling of sulphur, iron, carbon, and other elements. We discuss the biotechnological applications of aSRB in treating acid mine drainage (AMD, pH <3), focusing on their ability to produce biogenic sulphide and precipitate metals, particularly in the context of utilizing microbial consortia instead of pure isolates. Metal sulphide nanoparticles recovered after AMD treatment have multiple potential technological uses, including in electronics and biomedicine, contributing to a cost-effective circular economy. The products of aSRB metabolisms, such as biominerals and isotopes, could also serve as biosignatures to understand ancient and extant microbial life in the universe. Overall, aSRB are active components of the sulphur and carbon cycles under acidic conditions, with potential natural and technological implications for the world around us.

Biotechnological potential in agriculture of soil Antarctic microorganisms revealed by omics approach.

The biotechnological potential for agricultural applications in the soil in the thawing process on Whalers Bay, Deception Island, Antarctica was evaluated using a metagenomic approach through high-throughput sequencing. Approximately 22.70% of the sequences were affiliated to the phyla of the Bacteria dominion, followed by 0.26% to the Eukarya. Proteobacteria (Bacteria) and Ascomycota (Fungi) were the most abundant phyla. Thirty-two and thirty-six bacterial and fungal genera associated with agricultural biotechnological applications were observed. Streptomyces and Pythium were the most abundant genera related to the Bacteria and Oomycota, respectively. The main agricultural application associated with bacteria was nitrogen affixation; in contrast for fungi, was associated with phytopathogenic capabilities. The present study showed the need to use metagenomic technology to understand the dynamics and possible metabolic pathways associated with the microbial communities present in the soil sample in the process of thawing recovered from the Antarctic continent, which presented potential application in processes of agro-industrial interest.

Taxonomic and functional characterization of biofilms from a photovoltaic panel reveals high genetic and metabolic complexity of the communities.

AIMS: Biofilms are complex microbial cell aggregates that attach to different surfaces in nature, industrial environments, or hospital settings. In photovoltaic panels (PVs), biofilms are related to significant energy conversion losses. In this study, our aim was to characterize the communities of microorganisms and the genes involved in biofilm formation. METHODS AND RESULTS: In this study, biofilm samples collected from a PV system installed in southeastern Brazil were analyzed through shotgun metagenomics, and the microbial communities and genes involved in biofilm formation were investigated. A total of 2030 different genera were identified in the samples, many of which were classified as extremophiles or producers of exopolysaccharides. Bacteria prevailed in the samples (89%), mainly the genera Mucilaginibacter, Microbacterium, Pedobacter, Massilia, and Hymenobacter. The functional annotation revealed >12 000 genes related to biofilm formation and stress response. Genes involved in the iron transport and synthesis of c-di-GMP and c-AMP second messengers were abundant in the samples. The pathways related to these components play a crucial role in biofilm formation and could be promising targets for preventing biofilm formation in the PV. In addition, Raman spectroscopy analysis indicated the presence of hematite, goethite, and ferrite, consistent with the mineralogical composition of the regional soil and metal-resistant bacteria. CONCLUSIONS: Taken together, our findings reveal that PV biofilms are a promising source of microorganisms of industrial interest and genes of central importance in regulating biofilm formation and persistence.

Hyperexpansion of genetic diversity and metabolic capacity of extremophilic bacteria and archaea in ancient Andean lake sediments.

BACKGROUND: The Andean Altiplano hosts a repertoire of high-altitude lakes with harsh conditions for life. These lakes are undergoing a process of desiccation caused by the current climate, leaving terraces exposed to extreme atmospheric conditions and serving as analogs to Martian paleolake basins. Microbiomes in Altiplano lake terraces have been poorly studied, enclosing uncultured lineages and a great opportunity to understand environmental adaptation and the limits of life on Earth. Here we examine the microbial diversity and function in ancient sediments (10.3-11 kyr BP (before present)) from a terrace profile of Laguna Lejía, a sulfur- and metal/metalloid-rich saline lake in the Chilean Altiplano. We also evaluate the physical and chemical changes of the lake over time by studying the mineralogy and geochemistry of the terrace profile. RESULTS: The mineralogy and geochemistry of the terrace profile revealed large water level fluctuations in the lake, scarcity of organic carbon, and high concentration of SO42--S, Na, Cl and Mg. Lipid biomarker analysis indicated the presence of aquatic/terrestrial plant remnants preserved in the ancient sediments, and genome-resolved metagenomics unveiled a diverse prokaryotic community with still active microorganisms based on in silico growth predictions. We reconstructed 591 bacterial and archaeal metagenome-assembled genomes (MAGs), of which 98.8% belonged to previously unreported species. The most abundant and widespread metabolisms among MAGs were the reduction and oxidation of S, N, As, and halogenated compounds, as well as aerobic CO oxidation, possibly as a key metabolic trait in the organic carbon-depleted sediments. The broad redox and CO2 fixation pathways among phylogenetically distant bacteria and archaea extended the knowledge of metabolic capacities to previously unknown taxa. For instance, we identified genomic potential for dissimilatory sulfate reduction in Bacteroidota and α- and γ-Proteobacteria, predicted an enzyme for ammonia oxidation in a novel Actinobacteriota, and predicted enzymes of the Calvin-Benson-Bassham cycle in Planctomycetota, Gemmatimonadota, and Nanoarchaeota. CONCLUSIONS: The high number of novel bacterial and archaeal MAGs in the Laguna Lejía indicates the wide prokaryotic diversity discovered. In addition, the detection of genes in unexpected taxonomic groups has significant implications for the expansion of microorganisms involved in the biogeochemical cycles of carbon, nitrogen, and sulfur. Video Abstract.

Microbiota diversity of three Brazilian native fishes during ice and frozen storage.

This study aimed to assess the bacterial microbiota involved in the spoilage of pacu (Piaractus mesopotamics), patinga (female Piaractus mesopotamics x male Piaractus brachypomus), and tambacu (female Colossoma macropomum × male Piaractus mesopotamics) during ice and frozen storage. Changes in the microbiota of three fish species (N = 22) during storage were studied through 16S rRNA amplicon-based sequencing and correlated with volatile organic compounds (VOCs) and metabolites assessed by nuclear magnetic resonance (NMR). Storage conditions (time and temperature) affected the microbiota diversity in all fish samples. Fish microbiota comprised mainly of Pseudomonas sp., Brochothrix sp., Acinetobacter sp., Bacillus sp., Lactiplantibacillus sp., Kocuria sp., and Enterococcus sp. The relative abundance of Kocuria, P. fragi, L. plantarum, Enterococcus, and Acinetobacter was positively correlated with the metabolic pathways of ether lipid metabolism while B. thermosphacta and P. fragi were correlated with metabolic pathways involved in amino acid metabolism. P. fragi was the most prevalent spoilage bacteria in both storage conditions (ice and frozen), followed by B. thermosphacta. Moreover, the relative abundance of identified Bacillus strains in fish samples stored in ice was positively correlated with the production of VOCs (1-hexanol, nonanal, octenol, and 2-ethyl-1-hexanol) associated with off-flavors. 1H NMR analysis confirmed that amino acids, acetic acid, and ATP degradation products increase over (ice) storage, and therefore considered chemical spoilage index of fish fillets.

Gallium: a decisive "Trojan Horse" against microorganisms.

Controlling multidrug-resistant microorganisms (MRM) has a long history with the extensive and inappropriate use of antibiotics. At the cost of these drugs being scarce, new possibilities have to be explored to inhibit the growth of microorganisms. Thus, metallic compounds have shown to be promising as a viable alternative to contain pathogens resistant to conventional antimicrobials. Gallium (Ga3+) can be highlighted, which is an antimicrobial agent capable of disrupting the essential activities of microorganisms, such as metabolism, cellular respiration and DNA synthesis. It was observed that this occurs due to the similar properties between Ga3+ and iron (Fe3+), which is a fundamental ion for the correct functioning of bacterial activities. The mimetic effect performed by Ga3+ prevents iron transporters from distinguishing both ions and results in the substitution of Fe3+ for Ga3+ and in adverse metabolic disturbances in rapidly growing cells. This review focuses on analyzing the development of research involving Ga3+, elucidating the intracellular incorporation of the "Trojan Horse", summarizing the mechanism of interaction between gallium and iron and comparing the most recent and broad-spectrum studies using gallium-based compounds with antimicrobial scope.

Metagenomic Analysis to Assess the Impact of Plant Growth-Promoting Rhizobacteria on Peanut (Arachis hypogaea L.) Crop Production and Soil Enzymes and Microbial Diversity.

Peanut production could be increased through plant growth-promoting rhizobacteria (PGPR). In this regard, the present field research aimed at elucidating the impact of PGPR on peanut yield, soil enzyme activity, microbial diversity, and structure. Three PGPR strains (Bacillus velezensis, RI3; Bacillus velezensis, SC6; Pseudomonas psychrophila, P10) were evaluated, along with Bradyrhizobium japonicum (BJ), taken as a control. PGPR increased seed yield by 8%, improving the radiation use efficiency (4-14%). PGPR modified soil enzymes (fluorescein diacetate activity by 17% and dehydrogenase activity by 28%) and microbial abundance (12%). However, PGPR did not significantly alter microbial diversity; nonetheless, it modified the relative abundance of key phyla (Actinobacteria > Proteobacteria > Firmicutes) and genera (Bacillus > Arthrobacter > Pseudomonas). PGPRs modified the relative abundance of genes associated with N-fixation and nitrification while increasing genes related to N-assimilation and N-availability. PGPR improved agronomic traits without altering rhizosphere diversity.

Influence of the Chemical Properties of Cereal Grains on the Structure and Metabolism of the Bacteriome of Rhyzopertha dominica (F.) and Its Development: A Cause-Effect Analysis.

Rhyzopertha dominica causes significant economic losses in stored cereals. Insects' digestive tract microbiome is crucial for their development, metabolism, resistance, and digestion. This work aimed to test whether the different chemical properties of different wheat and barley grain cultivars cause disturbances in insect foraging and rearrangements of the structure of the R. dominica microbiome. The results indicated that grain cultivars significantly influence the microbiome, metabolism, and insect foraging. Most observed traits and microbiome structures were not correlated at the species level, as confirmed by ANOSIM (p = 0.441). However, the PLS-PM analysis revealed significant patterns within barley cultivars. The study found associations between C18:2 fatty acids, entomopathogenic bacteria, an impaired nitrogen cycle, lysine production of bacterial origin, and insect feeding. The antioxidant effects also showed trends towards impacting the microbiome and insect development. The findings suggest that manipulating grain chemical properties (increasing C18:2 and antioxidant levels) can influence the R. dominica microbiome, disrupting their foraging behaviours and adaptation to storage environments. This research supports the potential for breeding resistant cereals, offering an effective pest control strategy and reducing pesticide use in food production.

Analyzing the gut microbiota and microbial-associated metabolites of tomato-based sauces.

Red Cooked Sauce (RCS) and Red Raw Sauce (RRS) are a mixture of natural crops that have a promising content of bioactive compounds (BC). The aim was to determine the effect of the indigestible fraction (IF) during the colonic fermentation in RCS and RRS by studying the two-way relationship between gut microbiota composition and microbial metabolites produced from BC fermented in the TNO in vitro dynamic model of the human colon (TIM-2). Total BC in undigested and predigested RRS, 957 and 715 mg/100 g DW, respectively, was significantly higher (p < 0.05) than in the RCS, 571 and 406 mg/100 g DW, respectively. Catenibacterium and Holdemanella increased during RCS fermentation, while 13 genera showed a clear positive correlation with most microbial phenolic metabolites. Our findings suggest that the mechanisms, pathways, and enzymes involved in producing microbial metabolites exhibited uniqueness among bacterial taxa, even within shared genus/family classifications.

Estimating taxonomic and functional structure along a tropical estuary: linking metabolic traits and aspects of ecosystem functioning.

Microbial life forms are among the most ubiquitous on Earth, yet many remain understudied in Caribbean estuaries. We report on the prokaryote community composition of the Urabá Estuary in the Colombian Caribbean using 16S rRNA gene-transcript sequencing. We also assessed potential functional diversity through 38 metabolic traits inferred from 16S rRNA gene data. Water samples were collected from six sampling stations at two depths with contrasting light-penetration conditions along an approximately 100 km transect in the Gulf of Urabá in December 2019. Non-metric multidimensional scaling analysis grouped the samples into two distinct clusters along the transect and between depths. The primary variables influencing the prokaryote community composition were the sampling station, depth, salinity, and dissolved oxygen levels. Twenty percent of genera (i.e., 58 out 285) account for 95% of the differences between groups along the transect and among depths. All of the 38 metabolic traits studied showed some significant relationship with the tested environmental variables, especially salinity and except with temperature. Another non-metric multidimensional scaling analysis, based on community-weighted mean of traits, also grouped the samples in two clusters along the transect and over depth. Biodiversity facets, such as richness, evenness, and redundancy, indicated that environmental variations-stemming from river discharges-introduce an imbalance in functional diversity between surface prokaryote communities closer to the estuary's head and bottom communities closer to the ocean. Our research broadens the use of 16S rRNA gene transcripts beyond mere taxonomic assignments, furthering the field of trait-based prokaryote community ecology in transitional aquatic ecosystems.IMPORTANCEThe resilience of a dynamic ecosystem is directly tied to the ability of its microbes to navigate environmental gradients. This study delves into the changes in prokaryote community composition and functional diversity within the Urabá Estuary (Colombian Caribbean) for the first time. We integrate data from 16S rRNA gene transcripts (taxonomic and functional) with environmental variability to gain an understanding of this under-researched ecosystem using a multi-faceted macroecological framework. We found that significant shifts in prokaryote composition and in primary changes in functional diversity were influenced by physical-chemical fluctuations across the estuary's environmental gradient. Furthermore, we identified a potential disparity in functional diversity. Near-surface communities closer to the estuary's head exhibited differences compared to deeper communities situated farther away. Our research serves as a roadmap for posing new inquiries about the potential functional diversity of prokaryote communities in highly dynamic ecosystems, pushing forward the domain of multi-trait-based prokaryote community ecology.

Microbiota of arabica coffee: insights from soil to fruit.

Studies have shown that a diverse and metabolically active microbiota exists throughout different stages of coffee processing, from pre- to post-harvest. This microbiota originates from both the cultivation and processing environments. Additionally, microorganisms from the soil can be found on the fruit due to the transfer between them. This study reviews the microbiota present in Arabica coffee fruits and the soils where the plants are grown. It examines how microbial profiles are related to coffee variety, altitude, cultivation region, and processing method, and establishes a connection between the microbiota in soil and fruit. A diverse microbiota was observed in both coffee fruits and soils, with similar microorganisms identified across different growing regions, processing methods, and coffee varieties. However, exclusive detections of some microorganisms were also observed. These differences highlight the influence of terroir on coffee's microbial composition, confirming that environmental conditions, genetic factors, and processing methods shape coffee microbiota. Since microbial development during coffee fermentation can affect the beverage's quality, the data presented in this review offer valuable insights for researchers and producers. Understanding the influence of processing methods, coffee varieties, and cultivation regions on coffee microbiota enables the selection of specific fermentation conditions or starter cultures to enhance terroir characteristics or adjust microbial populations to favor or introduce microorganisms beneficial for coffee quality.

Genomic insights into organic acid production and plant growth promotion by different species of phosphate-solubilizing bacteria.

Bacteria can solubilize phosphorus (P) through the secretion of low-molecular-weight organic acids and acidification. However, the genes involved in the production of these organic acids are poorly understood. The objectives of this study were to verify the calcium phosphate solubilization and the production of low-molecular-weight organic acids by diverse genera of phosphate solubilizing bacterial strains (PSBS); to identify the genes related to the synthesis of the organic acids in the genomes of these strains and; to evaluate growth and nutrient accumulation of maize plants inoculated with PSBS and fertilized with Bayóvar rock phosphate. Genomic DNA was extracted for strain identification and annotation of genes related to the organic acids production. A greenhouse experiment was performed with five strains plus 150 mg dm- 3 P2O5 as Bayóvar rock phosphate (BRP) to assess phosphate solubilization contribution to maize growth and nutrition. Paraburkholderia fungorum UFLA 04-21 and Pseudomonas anuradhapurensis UFPI B5-8A solubilized over 60% of Ca phosphate and produced high amounts of citric/maleic and gluconic acids in vitro, respectively. Eleven organic acids were identified in total, although not all strains produced all acids. Besides, enzymes related to the organic acids production were found in all bacterial genomes. Plants inoculated with strains UFPI B5-6 (Enterobacter bugandensis), UFPI B5-8A, and UFLA 03-10 (Paenibacillus peoriae) accumulated more biomass than the plants fertilized with BRP only. Strains UFLA 03-10 and UFPI B5-8A increased the accumulation of most macronutrients, including P. Collectively, the results show that PSBS can increase maize growth and nutrient accumulation based on Bayóvar rock phosphate fertilization.

Environment and microbiome drive different microbial traits and functions in the macroscale soil organic carbon cycle.

Soil microbial traits and functions play a central role in soil organic carbon (SOC) dynamics. However, at the macroscale (regional to global) it is still unresolved whether (i) specific environmental attributes (e.g., climate, geology, soil types) or (ii) microbial community composition drive key microbial traits and functions directly. To address this knowledge gap, we used 33 grassland topsoils (0-10 cm) from a geoclimatic gradient in Chile. First, we incubated the soils for 1 week in favorable standardized conditions and quantified a wide range of soil microbial traits and functions such as microbial biomass carbon (MBC), enzyme kinetics, microbial respiration, growth rates as well as carbon use efficiency (CUE). Second, we characterized climatic and physicochemical properties as well as bacterial and fungal community composition of the soils. We then applied regression analysis to investigate how strongly the measured microbial traits and functions were linked with the environmental setting versus microbial community composition. We show that environmental attributes (predominantly the amount of soil organic matter) determined patterns of MBC along the gradient, which in turn explained microbial respiration and growth rates. However, respiration and growth normalized for MBC (i.e., specific respiration and growth) were more linked to microbial community composition than environmental attributes. Notably, both specific respiration and growth followed distinct trends and were related to different parts of the microbial community, which in turn resulted in strong effects on microbial CUE. We conclude that even at the macroscale, CUE is the result of physiologically decoupled aspects of microbial metabolism, which in turn is partially determined by microbial community composition. The environmental setting and microbial community composition affect different microbial traits and functions, and therefore both factors need to be considered in the context of macroscale SOC dynamics.

Optimizing intermittent micro-aeration as a strategy for enhancing aniline anaerobic biodegradation: kinetic, ecotoxicity, and microbial community dynamics analyses.

Groundwater and soil contamination by aromatic amines (AAs), used in the production of polymers, plastics, and pesticides, often results from improper waste disposal and accidental leaks. These compounds are resistant to anaerobic degradation; however, micro-aeration can enhance this process by promoting microbial interactions. In batch assays, anaerobic degradation of aniline (0.14 mM), a model AA, was tested under three micro-aeration conditions: T30, T15, and T10 (30, 15, and 10 min of micro-aeration every 2 h, respectively). Aniline degradation occurred in all conditions, producing both aerobic (catechol) and anaerobic (benzoic acid) byproducts. The main genera involved in T30 and T15 were Comamonas, Clostridium, Longilinea, Petrimonas, Phenylobacterium, Pseudoxanthomonas, and Thiobacillus. In contrast, in T10 were Pseudomonas, Delftia, Leucobacter, and Thermomonas. While T30 and T15 promoted microbial cooperation for anaerobic degradation and facultative respiration, T10 resulted in a competitive environment due to dominance and oxygen scarcity. Despite aniline degradation in 9.4 h under T10, this condition was toxic to Allium cepa seeds and exhibited cytogenotoxic effects. Therefore, T15 emerged as the optimal condition, effectively promoting anaerobic degradation without accumulating toxic byproducts. Intermittent micro-aeration emerges as a promising strategy for enhancing the anaerobic degradation of AA-contaminated effluents.

DNA stable isotope probing reveals the impact of trophic interactions on bioaugmentation of soils with different pollution histories.

BACKGROUND: Bioaugmentation is considered a sustainable and cost-effective methodology to recover contaminated environments, but its outcome is highly variable. Predation is a key top-down control mechanism affecting inoculum establishment, however, its effects on this process have received little attention. This study focused on the impact of trophic interactions on bioaugmentation success in two soils with different pollution exposure histories. We inoculated a 13C-labelled pollutant-degrading consortium in these soils and tracked the fate of the labelled biomass through stable isotope probing (SIP) of DNA. We identified active bacterial and eukaryotic inoculum-biomass consumers through amplicon sequencing of 16S rRNA and 18S rRNA genes coupled to a novel enrichment factor calculation. RESULTS: Inoculation effectively increased PAH removal in the short-term, but not in the long-term polluted soil. A decrease in the relative abundance of the inoculated genera was observed already on day 15 in the long-term polluted soil, while growth of these genera was observed in the short-term polluted soil, indicating establishment of the inoculum. In both soils, eukaryotic genera dominated as early incorporators of 13C-labelled biomass, while bacteria incorporated the labelled biomass at the end of the incubation period, probably through cross-feeding. We also found different successional patterns between the two soils. In the short-term polluted soil, Cercozoa and Fungi genera predominated as early incorporators, whereas Ciliophora, Ochrophyta and Amoebozoa were the predominant genera in the long-term polluted soil. CONCLUSION: Our results showed differences in the inoculum establishment and predator community responses, affecting bioaugmentation efficiency. This highlights the need to further study predation effects on inoculum survival to increase the applicability of inoculation-based technologies. Video Abstract.

A comparative genomic study of a hydrocarbon-degrading marine bacterial consortium.

Ocean oil pollution has a large impact on the environment and the health of living organisms. Bioremediation cleaning strategies are promising eco-friendly alternatives for tackling this problem. Previously, we designed and reported a hydrocarbon (HC) degrading microbial consortium of four marine strains belonging to the species Alloalcanivorax xenomutans, Halopseudomonas aestusnigri, Paenarthrobacter sp., and Pseudomonas aeruginosa. However, the knowledge about the metabolic potential of this bacterial consortium for HC bioremediation is not yet well understood. Here, we analyzed the complete genomes of these marine bacterial strains accompanied by a phylogenetic reconstruction along with 138 bacterial strains. Synteny between complete genomes of the same species or genus, revealed high conservation among strains of the same species, covering over 91% of their genomic sequences. Functional predictions highlighted a high abundance of genes related to HC degradation, which may result in functional redundancy within the consortium; however, unique and complete gene clusters linked to aromatic degradation were found in the four genomes, suggesting substrate specialization. Pangenome gain and loss analysis of genes involved in HC degradation provided insights into the evolutionary history of these capabilities, shedding light on the acquisition and loss of relevant genes related to alkane and aromatic degradation. Our work, including comparative genomic analyses, identification of secondary metabolites, and prediction of HC-degrading genes, enhances our understanding of the functional diversity and ecological roles of these marine bacteria in crude oil-contaminated marine environments and contributes to the applied knowledge of bioremediation.

Structural and functional bacterial biodiversity in a copper, zinc and nickel amended bioreactor: shotgun metagenomic study.

BACKGROUND: At lower concentrations copper (Cu), zinc (Zn) and nickel (Ni) are trace metals essential for some bacterial enzymes. At higher concentrations they might alter and inhibit microbial functioning in a bioreactor treating wastewater. We investigated the effect of incremental concentrations of Cu, Zn and Ni on the bacterial community structure and their metabolic functions by shotgun metagenomics. Metal concentrations reported in previous studies to inhibit bacterial metabolism were investigated. RESULTS: At 31.5 µM Cu, 112.4 µM Ni and 122.3 µM Zn, the most abundant bacteria were Achromobacter and Agrobacterium. When the metal concentration increased 2 or fivefold their abundance decreased and members of Delftia, Stenotrophomonas and Sphingomonas dominated. Although the heterotrophic metabolic functions based on the gene profile was not affected when the metal concentration increased, changes in the sulfur biogeochemical cycle were detected. Despite the large variations in the bacterial community structure when concentrations of Cu, Zn and Ni increased in the bioreactor, functional changes in carbon metabolism were small. CONCLUSIONS: Community richness and diversity replacement indexes decreased significantly with increased metal concentration. Delftia antagonized Pseudomonas and members of Xanthomonadaceae. The relative abundance of most bacterial genes remained unchanged despite a five-fold increase in the metal concentration, but that of some EPS genes required for exopolysaccharide synthesis, and those related to the reduction of nitrite to nitrous oxide decreased which may alter the bioreactor functioning.

Biomass Profiling in a Horizontal-Flow Anaerobic Bioreactor Used for Limonene Degradation.

This study characterized the microbial community present in the bench scale horizontal-flow anaerobic immobilized biomass bioreactor (HAIB) used in the removal of limonene, a compound present in citrus processing industries. The HAIB was filled with three support materials (coal, polyurethane foam and gravel) which were inoculated with anaerobic sludge. The limonene initial concentration on the substrate ranged from 10 mg/L to 500 mg/L. The analysis of 16S rRNA showed the presence of 22 OTUs (based on ⩾97% sequence identity), distributed in 57 genera, considering three different matrices. Higher relative abundance of phyla was observed as Synergistetes (43-57%), Proteobacteria (32-42%), Firmicutes (7-8%) and Acidobacteria (2-3%). Actinobacteria, Bacterioidetes and Chloroflexi had the lowest relative abundances between 1 and 2%. Synergistaceae family was the predominated group (47.6%-mineral coal, 55.9%-foam and 43.5%-gravel) followed by Syntrophaceae (2.4%-coal, 1.5%-foam and 2.2%-gravel), which kept a syntrophic relationship with methanogenesis (hydrogenotrophic methanogens) to maintain the anaerobic digestion. Among the Proteobacteria phylum, the Pseudomonadaceae family was predominant in the system with 12.0% on coal, 13.1% on foam, and 20.4% on gravel. The metabolic versatility of Pseudomonas sp. makes them an important bioremediation agent by being capable of metabolizing xenobiotic and chemical toxic compounds, thus having great prominence for the limonene removal in the HAIB bioreactor.

Bioremediation strategies against pesticides: An overview of current knowledge and innovations.

Pesticides pose significant risks to both human health, such as cancer, neurological disorders, and endocrine disruption, and ecosystems, through the destruction of beneficial insects, contamination of soil and water, and impact on non-target species. In the face of escalating pesticide pollution, there is an urgent need for multifaceted approaches to address the issue. Bioremediation emerges as a potent tool in the environmental pollution mitigation arsenal. Ideally aiming for the complete decomposition of pesticides into harmless molecules, bioremediation encompasses diverse approaches - from bioabsorption, bioadsorption, and biotransformation using enzymes and nanoenzymes to comprehensive degradation facilitated by microorganisms such as bacteria, fungi, macro- and microalgae, or phytoremediation. Exploring nature's biodiversity offers a promising avenue to find solutions to this pressing human-induced problem. The acceleration of biodegradation necessitates identifying and developing efficient organisms, achieved through bioprospection and targeted modifications. Specific strategies to enhance process efficiency and throughput include optimizing biomass production, strategic inoculation in diverse environments, and employing bioreactor systems for processing heavily contaminated waters or soils. This comprehensive review presents various bioremediation approaches, emphasizing the importance of microorganisms' exploration and new technologies development, including current innovations and patents to effectively combat pesticide pollution. Furthermore, challenges regarding the effective implementation of these technologies are also addressed.