Optimum Growth Temperature Research Articles

Growth Characterization of Bacillus sp. strain ZEID-14 on Acrylamide as the Sole Nitrogen Source

Acrylamide is a major pollution in soil from the breakdown of pesticides additive. Slowly but steadily, the use of microbe-mediated acrylamide breakdown as a bioremediation approach has gained attention all around the world. At room temperature, the effect of the initial pH on bacterial growth shows that the optimum pH range was discovered to be between 6.5 and 7.5. The optimal growing temperature at pH 7.5 ranged from 25 to 35 oC. In a series of experiments using a 1.0 percent (w/v) starting concentration of various organic carbon sources, it was determined that fructose, glucose and sucrose all supported the greatest amount of cellular growth on acrylamide. Acrylamide concentration of 500 mg/L promoted the most rapid expansion of growth, while levels of 1500 mg/L and higher entirely stopped growth. Mercury at 2 ppm caused 83% of inhibition whilst other metal ions such as copper, cadmium, lead and chromium showed minimal inhibition of less than 20% . The concentration of acrylamide and the time it took for this bacterium to start growing show an inverse relationship. A lag time of 1-3 days was found as the content of acrylamide was raised from 100 to 1000 mg/L while growth was abolished at 1500 mg/L. The maximal growth rate increased as acrylamide concentrations increased, indicating an overall trend of increased toxicity.
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Isolation and Growth Characterization of Staphylococcus sp. strain Amr-15 on Acrylamide as the Sole Nitrogen Source

Some of agricultural pesticides contained polyacrylamide as a dispersant and wetting agent. Polyacrylamide is slowly degraded to acrylamide, a suspected carcinogen and a neurotoxicant that has been documented to cause deaths of ruminants exposed to this compound. An acrylamide-degrading bacterium has been isolated from polluted soils in Egypt. The bacterium was identified partially as Staphylococcus sp. strain Amr-15 based on biochemical tests. At room temperature, the effect of the initial pH on bacterial growth shows that the optimum pH range was discovered to be between 7.0 and 7.5. The optimal growing temperature at pH 7.5 ranged from 25 to 40 degrees Celsius. In a series of experiments using a 1.0 percent (w/v) starting concentration of various organic carbon sources, it was determined that both glucose and sucrose supported the greatest amount of cellular growth on acrylamide. Acrylamide dosages of up to 2000 mg/L were explored as a single nitrogen supply. The greatest growth occurred between 300 and 1000 mg/L of acrylamide, resulting in a nearly 7.0 log CFU/mL increase with a nett growth of near 3 log CFU/mL when compared to the control. Growth was practically tolerated at the highest dosage tested, 2000 mg/L, and growth stopped entirely at 2500 mg/L. Mercury at 2 ppm caused 82% of inhibition whilst other metal ions such as copper, cadmium, lead and chromium show from 30 to 50% inhibition. The concentration of acrylamide and the time it took for this bacterium to start growing show an inverse relationship. A lag time of 1-3 days was found as the content of acrylamide was raised from 100 to 1000 mg/L while growth was abolished at 1500 mg/L. The maximal growth rate increased as acrylamide concentrations increased, indicating an overall trend of increased toxicity.

Parameterizing Vegetation Traits With a Process‐Based Ecohydrological Model and Xylem Water Isotopic Observations

AbstractKnowledge of plant hydraulic traits is critical for simulating terrestrial water storage, ecosystem water use, and tree responses to drought. The isotopic composition of tree xylem water (δXYLEM) has proven to be useful for understanding rooting strategies and for tracing terrestrial water flowpaths. Despite the broad collection of δXYLEM observations, few studies have estimated other plant traits from these data. We demonstrate the sensitivity of process‐based isotope‐enabled ecohydrological model (EcH2O‐iso) simulations of rooting depth distributions (KROOT), maximum stomatal conductance (gsMAX), optimal growth temperatures (TOPT), canopy light interception (KBEERS), stomatal sensitivity to vapor pressure deficits (gs‐VPD), and tree water storage capacity (TreeV) to δXYLEM observations. We sampled the δXYLEM of 30 Eastern hemlock (Tsuga canadensis) trees across 7 months, spanning a range of topographic positions and diameters. We calibrated the model 30 times with δXYLEM from each sampled tree. Calibrated values for gsMAX, KBEERS, and KROOT were validated with independent datasets of latent heat flux, canopy light interception, and xylem observations from independent hemlock stands. The calibrated values of several vegetation traits were significantly correlated with the diameters and topographic positions of the trees sampled in the field. These results indicate that δXYLEM reflects the characteristics and locations of the individual trees that are sampled, and therefore care must be taken in upscaling calibrated or measured plant traits for individual trees to larger horizontal scales. This research demonstrates that isotope‐enabled hydrological‐, land surface‐, and Earth systems‐models can leverage widely available water isotopic data to accurately estimate plant hydraulic traits.

Crystal structure of adenosine 5ʹ-phosphosulfate kinase isolated from Archaeoglobus fulgidus

The 3′-phosphoadenosine-5′-phosphosulfate (PAPS) molecule is essential during enzyme-catalyzed sulfation reactions as a sulfate donor and is an intermediate in the reduction of sulfate to sulfite in the sulfur assimilation pathway. PAPS is produced through a two-step reaction involving ATP sulfurylase and adenosine 5′-phosphosulfate (APS) kinase enzymes/domains. However, archaeal APS kinases have not yet been characterized and their mechanism of action remains unclear. Here, we first structurally characterized APS kinase from the hyperthermophilic archaeon Archaeoglobus fulgidus, (AfAPSK). We demonstrated the PAPS production activity of AfAPSK at the optimal growth temperature (83 °C). Furthermore, we determined the two crystal structures of AfAPSK: ADP complex and ATP analog adenylyl-imidodiphosphate (AMP-PNP)/Mg2+/APS complex. Structural and complementary mutational analyses revealed the catalytic and substrate recognition mechanisms of AfAPSK. This study also hints at the molecular basis behind the thermal stability of AfAPSK.

Hydrothermal growth of ZnO nanostructures with dopants Co2+, Ni2+ and Cu2+ - Structural and luminous characteristics

Transition metal doped ZnO: (Co/Ni/Cu) nanostructures grown using hydrothermal technique at an optimized growth temperature of 200 °C and a growth time of 3 hours exhibit violet photoluminescence emission. The scanning electron micrographs recorded from the as synthesized samples (ZnO:Co, ZnO:Ni and ZnO:Cu) display nanorods, nanosheet and nanoflower morphology depending upon the dopant/doping percentage. The X-ray diffraction and Raman analysis confirm that hexagonal wurtzite structure of ZnO is retained even after nominal doping of Co, Ni and Cu ions. Optical properties of hydrothermally grown ZnO crystals were analysed with respect to doping concentration (3, 4 and 5 wt%) of Co, Ni and Cu. The optical band gap of ZnO:Co decreases with increasing doping concentration, where as in the case of ZnO:Ni and ZnO:Cu, the band gap increases with increasing the doping concetration. Intense violet deep level emission was observed from ZnO:Co, ZnO:Ni and ZnO:Cu samples at room temperature and the intensity of violet luminescence decreased with increasing the doping concentration of Co2+, Ni2+ and Cu2+ ions into ZnO.

Are we underestimating the ecological and evolutionary effects of warming? Interactions with other environmental drivers may increase species vulnerability to high temperatures

Warming, the most prominent aspect of global environmental change, already affects most ecosystems on Earth. In recent years, biologists have increasingly integrated the effects of warming into their models by capturing how temperature shapes their physiology, ecology, behavior, evolutionary adaptation and probability of extirpation/extinction. The more physiologically‐grounded approaches to predicting ectotherms' responses use thermal performance curves (TPCs) obtained by measuring species performance (e.g. growth rate) under different temperatures. TPCs are typically measured while other factors are held constant at benign levels to ‘isolate' the effects of temperature. Here we highlight that this practice paints a misleading picture because TPCs are functions of other factors, including global change stressors. We review evidence that resource limitation, pH, oxygen and CO2 concentration, salinity, water availability, parasites and mutualists, all influence TPC shape and thermal traits such as optimum temperature for growth. Evidence from a wide variety of organisms – phytoplankton, protists, plants, insects and fish – points towards such interactions increasing organisms' susceptibility to high temperatures (reducing it in the case of mutualists). Failing to account for these interactions is likely to lead to erroneous predictions of performance in nature and an underestimation of the risks of warming. We discuss the general patterns and possible consequences of such interactions for ecological communities. But importantly, interactions with TPCs share common features that we can learn from. Incorporating these interactions into population and community models should lead to deeper insights and more accurate predictions of species' performance in nature – as well as strategies for managing natural and agricultural ecosystems in the face of warming.

Comparison of prokaryotes between Mount Everest and the Mariana Trench

BackgroundMount Everest and the Mariana Trench represent the highest and deepest places on Earth, respectively. They are geographically separated, with distinct extreme environmental parameters that provide unique habitats for prokaryotes. Comparison of prokaryotes between Mount Everest and the Mariana Trench will provide a unique perspective to understanding the composition and distribution of environmental microbiomes on Earth.ResultsHere, we compared prokaryotic communities between Mount Everest and the Mariana Trench based on shotgun metagenomic analysis. Analyzing 25 metagenomes and 1176 metagenome-assembled genomes showed distinct taxonomic compositions between Mount Everest and the Mariana Trench, with little taxa overlap, and significant differences in genome size, GC content, and predicted optimal growth temperature. However, community metabolic capabilities exhibited striking commonality, with > 90% of metabolic modules overlapping among samples of Mount Everest and the Mariana Trench, with the only exception for CO2 fixations (photoautotrophy in Mount Everest but chemoautotrophy in the Mariana Trench). Most metabolic pathways were common but performed by distinct taxa in the two extreme habitats, even including some specialized metabolic pathways, such as the versatile degradation of various refractory organic matters, heavy metal metabolism (e.g., As and Se), stress resistance, and antioxidation. The metabolic commonality indicated the overall consistent roles of prokaryotes in elemental cycling and common adaptation strategies to overcome the distinct stress conditions despite the intuitively huge differences in Mount Everest and the Mariana Trench.ConclusionOur results, the first comparison between prokaryotes in the highest and the deepest habitats on Earth, may highlight the principles of prokaryotic diversity: although taxa are habitat-specific, primary metabolic functions could be always conserved.8c6sxptuhXFJaznJoiBvg_Video abstract.

Effects of Water Temperature on the Growth, Antioxidant Capacity, and Gut Microbiota of Percocypris pingi Juveniles

It is necessary to determine the optimal temperature for Percocypris pingi growth in recirculating aquaculture systems. To describe the effects of temperature, we evaluated the growth, antioxidant enzyme activity, and gut microbiota structure of P. pingi at different temperatures, including 14, 18, 22, and 26 °C. Results showed that increases in body weight of individuals of the groups subjected to 18 and 22 °C temperatures were considerably higher than those in the groups subjected to temperatures of 14 and 26 °C between 20 and 60 d after the experiment started. Acid phosphatase activity in the liver and kidneys of P. pingi did not differ significantly among the various temperature groups (p > 0.05). A gradual restoration of the alkaline phosphatase and superoxide dismutase activities to variations in the surrounding temperature was observed in the liver and kidney of P. pingi. Interestingly, the water temperature did not affect the α-diversity or composition of the gut microbiota of P. pingi. In conclusion, water temperatures between 14 and 26 °C significantly impacted the growth of P. pingi (p < 0.05) but not the liver and kidney antioxidant capacity or the gut microbiota within 60 d.

Transcriptional differences between major Fusarium pathogens of maize, Fusarium verticillioides and Fusarium graminearum with different optimum growth temperatures.

Fusarium verticillioides and Fusarium graminearum are important pathogens causing disease in maize (Zea mays) worldwide. The distributions of these fungal pathogens vary greatly in different regions and in different years, and are influenced by environmental and climatic conditions. Temperature has significant effects on the growth and mycotoxin production of Fusarium species. In this study, the effects of temperature on the growth and pathogenicity of F. verticillioides and F. graminearum were investigated. F. verticillioides grew fastest and exhibited the strongest pathogenicity to maize stems and grains at 30°C, while F. graminearum grew best at 20°C. Both species produced more toxins at 20°C than at 30°C. To explain the interspecific differences in the relationship of growth and temperature, RNA-seq was used to compare F. verticillioides and F. graminearum cultivated for 4 d at the optimum temperatures of 30°C and 20°C, respectively. Samples of F. verticillioides were also cultivated for 9 d (to maximize toxin production) at 20°C and 30°C and analyzed by RNA-seq to investigate the influence of temperature for different growth stages. The differently expressed genes (DEGs) were identified by comparison of cultures grown for the same amount of time but at different temperatures. GO enrichment analysis showed high enrichment of DEGs in categories of membrane part, catalytic activity, metabolic process, and growth at warmer temperature resulted in more down-regulated DEGs enriched in membrane components in all groups. KEGG analysis revealed enrichment of DEGs related to different temperatures in carbohydrate and amino acid metabolism pathways. For both species, there was decreased expression of many DEGs related to amino acid metabolism when cultivated at warm temperature, such as genes related to beta-alanine metabolism and arginine and proline metabolism. However, changes in genes related to glyoxylate and dicarboxylate metabolism and fatty acid degradation were more related to the growth state. The results showing different responses pattern of these pathways provides a foundation for further investigation of the molecular mechanisms underlying distinct thermal ecological niches of F. verticillioides and F. graminearum.

Microbial saccharification – Biorefinery platform for lignocellulose

Lignocellulosic biomass has gained increasing attention as it can be bio-transformed into biofuel, such as bioethanol , biobutanol, biohydrogen, biogas and biodiesel . The conventional strategy includes the biotransformation of lignocellulose into soluble and fermentable sugars through enzymatic hydrolysis for bioenergy production. However, the exogenous cellulase reagent preparation leads to increased complexity and a high saccharification cost. Microbial saccharification (MS) can also realize in-situ simultaneous enzymatic production and hydrolysis to obtain value-added products in a single step. However, its application is limited due to the high temperature of enzymatic hydrolysis than the optimum growth and enzyme synthesis temperature of most natural microorganisms. Nevertheless, some microbial strains and consortiums with excellent potential for microbial saccharification have been discovered and developed. Therefore, this review comprehensively summarizes different microorganisms with MS strategies, including natural and modified strains, the limitations of different strains, and possibilities for industrial application. • Compare the microbial saccharification of lignocellulosic biomass by different microorganisms. • Most bacteria mainly degrade hemicellulose while fungi degrade cellulose. • Mix enzymes/fungi promote microbial saccharification of lignocellulosic biomass. • Industrial application of microbial saccharification for biofuels production.

Identification and utilization of a new Bacillus amyloliquefaciens XY-1 against Fusarium head blight.

Fusarium head blight (FHB) is a global wheat grain disease caused by Fusarium graminearum. Biological control of FHB is considered to be an alternative disease management strategy that is environmentally benign, durable, and compatible with other control measures. In this study, to screen antagonistic bacteria with the potential to against FHB, 45 strains were isolated from different tissues of wheat. Among them, seven strains appeared to effectively inhibit F. graminearum growth, the antagonistic bacterium named XY-1 showed a highly antagonistic effect against FHB using dual culture assays. The strain XY-1 was identified as Bacillus amyloliquefaciens by 16S rDNA sequence. Antibiotic tolerance of antagonistic bacteria showed that XY-1 had antagonistic activity against Colletotrichum gloeosporioides, Rhizoctonia solani, Sclerotium rolfsii, and Alternaria alternata. Nutrition tests showed that the most suitable carbon and nitrogen sources were glucose and beef extract, respectively. The optimum growth temperature and pH value were 28 ℃ and 7.4. Antibiotics tolerance cultivation showed that XY-1 had strong resistance to Chloramphenicol and Ampicillin. Wheat spikes inoculation antagonism tests showed that strain XY-1 displayed strong antifungal activity against F. graminearum. Our study laid a theoretical foundation for the application of strain XY-1 as a biological agent in the field to control FHB.

Growth Rates of Vibrio parahaemolyticus Sequence Type 36 Strains in Live Oysters and in Culture Medium.

The pathogenic marine bacterium Vibrio parahaemolyticus can cause seafood-related gastroenteritis via the consumption of raw or undercooked seafood. Infections originating from relatively cool waters in the northeast United States are typically rare, but recently, this region has shown an increase in infections attributed to the ecological introduction of pathogenic sequence type 36 (ST36) strains, which are endemic to the cool waters of the Pacific Northwest. A 2005 risk assessment performed by the Food and Drug Administration (FDA) modeled the postharvest growth of V. parahaemolyticus in oysters as a function of air temperature and the length of time the oysters remained unrefrigerated. This model, while useful, has raised questions about strain growth differences in oyster tissue and whether invasive pathogenic strains exhibit different growth rates than nonclinical strains, particularly at lower temperatures. To investigate this question, live eastern oysters were injected with ST36 clinical strains and non-ST36 nonclinical strains, and growth rates were measured using the most probable number (MPN) enumeration. The presence of V. parahaemolyticus was confirmed using PCR by targeting the thermolabile hemolysin gene (tlh), thermostable direct hemolysin (tdh), tdh-related hemolysin (trh), and a pathogenesis-related protein (prp). The growth rates of the ST36 strains were compared to the FDA model and several other data sets of V. parahaemolyticus growth in naturally inoculated oysters harvested from the Chesapeake Bay. Our data indicate that the growth rates from most studies fall within the mean of the FDA model, but with slightly higher growth at lower temperatures for ST36 strains injected into live oysters. These data suggest that further investigations of ST36 growth capability in oysters at temperatures previously thought unsuitably low for Vibrio growth are warranted. IMPORTANCE Vibrio parahaemolyticus is the leading cause of seafood-related gastroenteritis in the United States, with an estimated 45,000 cases per year. Most individuals who suffer from vibriosis consume raw or undercooked seafood, including oysters. While gastroenteritis vibriosis is usually self-limiting and treatable, V. parahaemolyticus infections are a stressor on the growing aquaculture industry. Much effort has been placed on modeling the growth of Vibrio cells in oysters in order to aid oyster growers in designing harvesting best practices and ultimately, to protect the consumer. However, ecological invasions of nonnative bacterial strains make modeling their growth complicated, as these strains are not accounted for in current models. The National Shellfish Sanitation Program (NSSP) considers 10°C (50°F) a temperature too low to enable Vibrio growth, where 15°C is considered a cutoff temperature for optimal Vibrio growth, with temperatures approaching 20°C supporting higher growth rates. However, invasive strains may be native to cooler waters. This research aimed to understand strain growth in live oysters by measuring growth rates when oysters containing ST36 strains, which may be endemic to the U.S. Pacific Northwest, were exposed to multiple temperatures postharvest. Our results will be used to aid future model development and harvesting best practices for the aquaculture industry.

Biodegradation of Cyanide by a New Isolated Aerococcus viridans and Optimization of Degradation Conditions by Response Surface Methodology

Microbial treatment of cyanide pollution is an effective, economical, and environmentally friendly method compared with physical or chemical approaches. A cyanide-degrading bacterium was isolated from electroplating sludge and identified as Aerococcus viridans (termed A. viridans T1) through an analysis of the biochemical reaction and 16 S rDNA gene sequence. A. viridans T1 showed a maximum resistance to 550 mg L−1 CN−. The effect of pH and temperature on cyanide degradation and bacterial growth was evaluated. The highest cyanide removal efficiency and bacterial growth occurred at pH 8 and pH7, respectively. The optimum temperature for cyanide degradation and bacterial growth was 34 ∘C. In addition, the carbon source and nitrogen source for cyanide degradation were optimized. The optimal carbon source and nitrogen source were glycerol and peptone, respectively. The cyanide degradation experiment indicated that A. viridans T1 was able to remove 84.1% of free cyanide at an initial concentration of 200 mg L−1 CN− within 72 h and 86.7% of free cyanide at an initial concentration of 150 mg L−1 CN− within 56 h. To improve the cyanide-degrading efficiency of A. viridans T1, eight process variables were further optimized using a response surface methodology. Three significant variables (soybean meal, corn flour, and L-cysteine) were identified using a Plackett–Burman design, and the variable levels were optimized using a central composite design. The optimal values of soybean meal, corn flour, and L-cysteine were 1.11%, 1.5%, and 1.2%, respectively. Under these optimal conditions, the confirmatory experiments showed that the actual degradation rate was 97.3%, which was similar to the predicted degradation rate of 98.87%. Its strong resistance to cyanide and cyanide-degrading activity may allow A. viridans T1 to be a candidate for the bioremediation of cyanide-contaminated environments.

A new embryonic cell line YCE1 from large yellow croaker (Larimichthys crocea) and its susceptibility to large yellow croaker iridovirus

In order to develop in vitro culture models for the viral pathogens found in large yellow croaker (Larimichthys crocea), a new cell line derived from L. crocea embryo, YCE1, was established and characterized. This cell line has been maintained in vitro for over 24 months, and subcultured for >80 times in a Leibovitz's L-15 medium supplemented with fetal bovine serum (FBS). The YCE1 cells, which were identified to be predominantly fibroblast-like by immunofluorescence, are able to form a monolayer at 15–37 °C, with an optimum growth temperature of 26 °C. In the chromosome analysis, the YCE1 cells exhibited to be highly heteroploid. The green fluorescence protein (GFP) reporter gene was successfully expressed in the YCE1 cells. In the susceptibility test with regard to large yellow croaker iridovirus (LYCIV) in the YCE1 cells, noticeable and stable cytopathic effects (CPEs) were found in a host-origin cell line for the first time. In addition, a special intracellular pattern of the immature viral particles contained in vesicular organelles was confirmed by transmission electron microscopy, suggesting that the YCE1 cell line could serve as a viable tool for the investigation of host-pathogen interaction of LYCIV and other related megalocytiviruses.

Learning deep representations of enzyme thermal adaptation.

Temperature is a fundamental environmental factor that shapes the evolution of organisms. Learning thermal determinants of protein sequences in evolution thus has profound significance for basic biology, drug discovery, and protein engineering. Here, we use a data set of over 3 million BRENDA enzymes labeled with optimal growth temperatures (OGTs) of their source organisms to train a deep neural network model (DeepET). The protein-temperature representations learned by DeepET provide a temperature-related statistical summary of protein sequences and capture structural properties that affect thermal stability. For prediction of enzyme optimal catalytic temperatures and protein melting temperatures via a transfer learning approach, our DeepET model outperforms classical regression models trained on rationally designed features and other deep-learning-based representations. DeepET thus holds promise for understanding enzyme thermal adaptation and guiding the engineering of thermostable enzymes.

Sub‐seasonal correlation between growth and survival in three sympatric aquatic ectotherms

Animals experience seasonally changing conditions in temperate regions, thus population vital rates change seasonally. However, knowledge is lacking on patterns of seasonal correlation between growth and survival in sympatric ectotherms, and this knowledge gap limits our understanding of environmental change impacts on animal populations and communities. Here, we investigated sub‐seasonal (two‐month intervals) correlation between growth and survival in three stream fishes (bluehead chubNocomis leptocephalus, creek chubSemotilus atromaculatusand mottled sculpinCottus bairdii) in South Carolina, USA, via a mark–recapture survey over 28 months. We found that patterns of temporal correlation between the population vital rates differed among the sympatric species. Growth increased and survival decreased with water temperature in two eurythermal species, resulting in negative correlation between growth and survival. Growth peaked in sub‐seasons with an intermediate water temperature range in a third stenothermal species, while survival decreased with water temperature for this species too. Consequently, there was not significant negative or positive correlation between sub‐seasonal growth and survival in the stenothermal species. Body condition (weight at given length) decreased from May through November in all three species, providing a potential physiological explanation for why survival rates were lower during this period. Negative correlation among population vital rates stabilizes population size over time and buffers animal populations from environmental change because the vital rates are not affected simultaneously in the same direction, indicating some degree of resiliency in the face of climate changes in the two eurythermal species. However, such a demographic mechanism of resiliency could be maintained so long as climate warming does not exceed optimal growth temperature, above which negative correlation between growth and survival may no longer be maintained.

Taxonomic and Biochemical Characterization of Microalga Graesiella emersonii GEGS21 for Its Potential to Become Feedstock for Biofuels and Bioproducts

Graesiella emersonii is a commercially exploitable source of bioactive compounds and biofuels with potential applications in microalgae-based industries. Despite this, little taxonomical information is available. Therefore, proper identification and characterization are needed for the sustainable utilization of isolated microalgae. In this study, an axenically isolated unicellular green alga from the Geumgang Estuary, Korea was investigated for its morphological, molecular, and biochemical characteristics. The morphological characteristics were typical of G. emersonii. Molecular phylogenetic analysis of the 18S rDNA sequence verified that the isolate belonged to G. emersonii and was subsequently named G. emersonii GEGS21. It was isolated from brackish water, and its optimal growth temperature, salinity, and light intensity were at 28–32 °C, 0 M NaCl, and 130–160 µmol m−2 s−1, respectively. The strain thrived over a range of temperatures (5–40 °C) and withstood up to 0.5 M NaCl. The isolate was rich in omega-6 linoleic acid (C18:2 n-6, 26.3%) and palmitic acid (C16:0, 27.5%). The fuel quality properties were determined, and biodiesel from GEGS21 could be used as a biodiesel blend. Value-added carotenoids lutein (1.5 mg g−1 dry cell weight, DCW) and neoxanthin (1.2 mg g−1 DCW) were biosynthesized as accessory pigments by this microalga. The biomass of this microalga may serve as feedstock for biodiesel production as well as producing valuable ω-6 and carotenoids.

Complete genome sequence analysis of a novel alkane-degrading bacterial strain, Acinetobacter vivianii KJ-1, and its diesel degradation ability

With the increasing demand for diesel in various countries, the ecological pollution caused by the improper use, storage, and accidental leakage of diesel needs to be addressed urgently. As an environmentally friendly and cost-effective method, bioremediation generally uses various microorganisms to remove pollutants from the environment. Here, the strain KJ-1, obtained through an enrichment culture using n-dodecane from oil-contaminated soil near a gas station as the substrate, was identified as Acinetobacter vivianii according to its morphology, biochemistry, and molecular biology. The isolate KJ-1 was able to use diesel as a sole carbon source and more than 40% of diesel was degraded after 12 days of incubation with strain KJ-1 in mineral salts medium. The most suitable diesel concentration and nitrogen source concentrations were 4,140 mg/L and 350–700 mg/L, respectively, for diesel degradation and bacterial growth. The optimal initial pH and temperature for strain KJ-1 growth and diesel degradation were 6.5–8.0 and 20–37°C, respectively. To investigate the diesel-degrading mechanisms of this strain, the complete genome was sequenced and annotated. The complete genome consists of one chromosome with a total length of 3,927,757 base pairs and a G + C content of 41.5%. The genes related to the two-component regulatory system and alkane degradation were analyzed. In addition, two putative alkane monooxygenases were analyzed, and the protein sequences were characterized and compared with other AlkBs in Acinetobacter spp. using sequences downloaded from NCBI. The results demonstrated that A. vivianii KJ-1 may be particularly useful for future bioremediation of diesel-polluted soil.

Identification of hydrocarbon-degrading bacterial consortium isolated from the oil-contaminated muddy soil in Hanoi, Vietnam

Bioremediation is a promising approach for treating oil-contaminated environments. The main objective of this study was to isolate bacteria capable of degrading hydrocarbons for application in oily wastewater treatment from oil-contaminated sites in Hanoi, Vietnam. The bacterial consortium studied was obtained from an oil-contaminated muddy soil sample enriched with crude oil mixed with diesel oil as a carbon source. The reconstituted consortium was able to degrade 93% of the oil content after 7 days of testing. A total of five pure bacterial strains were isolated on TSA agar from the complex microbial communities and were selected as potential candidates for oily sludge biodegradation processes. These isolates were identified based on their morphological and biochemical characteristics. By using molecular biology techniques, five hydrocarbons degrading bacteria were investigated and identified as Pseudomonas mendocina strain MD1 (OL687411.1), Pseudomonas hydrolytica strain MD2 (OL771695.1), Brucella intermedia strain MD3 (OL687412.1), Pseudomonas stutzeri strain MD4 (OL687413.1), and Stenotrophomonas nitritireducens strain MD5 (OL687414.1). The morphological and biochemical characterization of these bacteria showed that five of them were Gram-negative, rod-shaped, catalase positive, the ideal pH was neutral, and the optimum growth temperature was 30ºC in a culture medium with a salinity of 0.5%. These strains are capable of producing extracellular enzymes, such as lipase, amylase, cellulase, and protease.

A genomic approach to analyze the cold adaptation of yeasts isolated from Italian Alps.

Microorganisms including yeasts are responsible for mineralization of organic matter in cold regions, and their characterization is critical to elucidate the ecology of such environments on Earth. Strategies developed by yeasts to survive in cold environments have been increasingly studied in the last years and applied to different biotechnological applications, but their knowledge is still limited. Microbial adaptations to cold include the synthesis of cryoprotective compounds, as well as the presence of a high number of genes encoding the synthesis of proteins/enzymes characterized by a reduced proline content and highly flexible and large catalytic active sites. This study is a comparative genomic study on the adaptations of yeasts isolated from the Italian Alps, considering their growth kinetics. The optimal temperature for growth (OTG), growth rate (Gr), and draft genome sizes considerably varied (OTG, 10°C-20°C; Gr, 0.071-0.0726; genomes, 20.7-21.5 Mpb; %GC, 50.9-61.5). A direct relationship was observed between calculated protein flexibilities and OTG, but not for Gr. Putative genes encoding for cold stress response were found, as well as high numbers of genes encoding for general, oxidative, and osmotic stresses. The cold response genes found in the studied yeasts play roles in cell membrane adaptation, compatible solute accumulation, RNA structure changes, and protein folding, i.e., dihydrolipoamide dehydrogenase, glycogen synthase, omega-6 fatty acid, stearoyl-CoA desaturase, ATP-dependent RNA helicase, and elongation of very-long-chain fatty acids. A redundancy for several putative genes was found, higher for P-loop containing nucleoside triphosphate hydrolase, alpha/beta hydrolase, armadillo repeat-containing proteins, and the major facilitator superfamily protein. Hundreds of thousands of small open reading frames (SmORFs) were found in all studied yeasts, especially in Phenoliferia glacialis. Gene clusters encoding for the synthesis of secondary metabolites such as terpene, non-ribosomal peptide, and type III polyketide were predicted in four, three, and two studied yeasts, respectively.