Identification of enzyme-producing thermophilic bacilli isolated from marine vents of Aeolian Islands (Italy)

Diver Underwater Cycling Endurance After Short-Term Warm and Hot Water Acclimation

INTRODUCTION

It is unclear whether immersion heat acclimation benefits exercise in warm water conditions. This study examined the effects of heat acclimation strategies on heart rate (HR), core temperature, and time to exhaustion (TTE) during cycling exercise in varying warm water conditions.

METHODS

Twenty male divers completed this study at the Navy Experimental Diving Unit. Subjects were randomly assigned to one of two 9-day heat acclimation groups. The first group (WARM; n = 10) cycled for 2 hours at 50 W in 34.4 °C water, while the second group (HOT; n = 10) cycled for 1 hour against minimal resistance in 36.7 °C water. Following acclimation, TTE was tested by underwater cycling (30 W) in 35.8 °C, 37.2 °C, and 38.6 °C water.

RESULTS

Throughout acclimation, the rate of core temperature rise in the first 30 minutes of exercise increased (P = .02), but the maximum core temperature reached was not different for either group. Time to exhaustion (TTE) was reduced, and the rate of core temperature rise during performance testing increased (both P < .001) with increasing water temperature but was not different between groups. Core temperature and HR increased throughout performance testing in each water condition and were lower in the HOT compared to the WARM acclimation group (all P < .05) with the exception of core temperature in the 37.2 °C condition.

CONCLUSIONS

Underwater exercise performance did not differ between the two acclimation strategies. This study suggests that passive acclimation to a higher water temperature may improve thermoregulatory and cardiovascular responses to exercise in warm water. Hot water immersion adaptations are dependent on exercise intensity and water temperature.

Mapping the microbial diversity associated with different geochemical regimes in the shallow-water hydrothermal vents of the Aeolian archipelago, Italy

Shallow-water hydrothermal vents are unique marine environments ubiquitous along the coast of volcanically active regions of the planet. In contrast to their deep-sea counterparts, primary production at shallow-water vents relies on both photoautotrophy and chemoautotrophy. Such processes are supported by a range of geochemical regimes driven by different geological settings. The Aeolian archipelago, located in the southern Tyrrhenian sea, is characterized by intense hydrothermal activity and harbors some of the best sampled shallow-water vents of the Mediterranean Sea. Despite this, the correlation between microbial diversity, geochemical regimes and geological settings of the different volcanic islands of the archipelago is largely unknown. Here, we report the microbial diversity associated with six distinct shallow-water hydrothermal vents of the Aeolian Islands using a combination of 16S rRNA amplicon sequencing along with physicochemical and geochemical measurements. Samples were collected from biofilms, fluids and sediments from shallow vents on the islands of Lipari, Panarea, Salina, and Vulcano. Two new shallow vent locations are described here for the first time. Our results show the presence of diverse microbial communities consistent in their composition with the local geochemical regimes. The shallow water vents of the Aeolian Islands harbor highly diverse microbial community and should be included in future conservation efforts.

Ecological and Biotechnological Relevance of Mediterranean Hydrothermal Vent Systems

Marine hydrothermal systems are a special kind of extreme environments associated with submarine volcanic activity and characterized by harsh chemo-physical conditions, in terms of hot temperature, high concentrations of CO2 and H2S, and low pH. Such conditions strongly impact the living organisms, which have to develop adaptation strategies to survive. Hydrothermal systems have attracted the interest of researchers due to their enormous ecological and biotechnological relevance. From ecological perspective, these acidified habitats are useful natural laboratories to predict the effects of global environmental changes, such as ocean acidification at ecosystem level, through the observation of the marine organism responses to environmental extremes. In addition, hydrothermal vents are known as optimal sources for isolation of thermophilic and hyperthermophilic microbes, with biotechnological potential. This double aspect is the focus of this review, which aims at providing a picture of the ecological features of the main Mediterranean hydrothermal vents. The physiological responses, abundance, and distribution of biotic components are elucidated, by focusing on the necto-benthic fauna and prokaryotic communities recognized to possess pivotal role in the marine ecosystem dynamics and as indicator species. The scientific interest in hydrothermal vents will be also reviewed by pointing out their relevance as source of bioactive molecules.

Partial consolidated bioprocessing of pretreated Pennisetum sp. by anaerobic thermophiles for enhanced bioethanol production

Rapid industrialization and consumption of fossil fuels have led to considerable progress in the production of renewable biofuels like bioethanol. Lignocellulosic biomass such as grasses serves as cheap feedstocks for the production of bioethanol. However, the process involved in lignocellulosic bioethanol production is expensive which restricts its industrial production. The present study thus attempted to investigate a partially consolidated bioprocessing (PCB) approach using two isolated anaerobic thermophiles i.e. Bacillus paranthracis and Bacillus nitratireducens for direct conversion of ultra-sonication assisted sodium hydroxide (UA-NaOH) pretreated Denannath grass to bioethanol in co-culture consortium batch fermentation experiments. The process parameters for the PCB approach were optimized using the Box-Behnken design of Response Surface Methodology (RSM). The parameters that were considered were substrate concentration (5-10 g), incubation time (30-66 h), inoculum volume [1:1 to 3:3 (% v/v) and temperature (50-65 °C). The maximum ethanol concentration of 8.46 mM (0.39 g/L from 7.5 g/L of substrate loading) and ethanol yield (Yp/s) of 0.55 g/g of reducing sugar was obtained at 57.5 °C. In the same conditions the cellulase and xylanase activities were 0.8 U/mL and 11.53 U/mL respectively, while the lactate and acetate concentrations were 0.2 mM (0.009 g/L) and 2.9 mM (0.13 g/L) correspondingly. An increase in the substrate loadings to 250 g/L in a batch fermenter (3 L) resulted in the production of 373.35 mM (17.1 g/L) of ethanol concentration and Yp/s of 0.16 g/g of reducing sugar.

Divers risk accelerated fatigue and core temperature rise during fully-immersed exercise in warmer water temperature extremes

Physiological responses to work in cold water have been well studied but little is known about the effects of exercise in warm water; an overlooked but critical issue for certain military, scientific, recreational, and professional diving operations. This investigation examined core temperature responses to fatiguing, fully-immersed exercise in extremely warm waters. Twenty-one male U.S. Navy divers (body mass, 87.3 ± 12.3 kg) were monitored during rest and fatiguing exercise while fully-immersed in four different water temperatures (Tw): 34.4, 35.8, 37.2, and 38.6°C (Tw_34.4, Tw_35.8, Tw_37.2, and Tw_38.6 respectively). Participants exercised on an underwater cycle ergometer until volitional fatigue or core temperature limits were reached. Core body temperature and heart rate were monitored continuously. Trial performance time decreased significantly as water temperature increased (Tw_34.4, 174 ± 12 min; Tw_35.8, 115 ± 13 min; Tw_37.2, 50 ± 13 min; Tw_38.6, 34 ± 14 min). Peak core body temperature during work was significantly lower in Tw_34.4 water (38.31 ± 0.49°C) than in warmer temperatures (Tw_35.8, 38.60 ± 0.55°C; Tw_37.2, 38.82 ± 0.76°C; Tw_38.6, 38.97 ± 0.65°C). Core body temperature rate of change increased significantly with warmer water temperature (Tw_34.4, 0.39 ± 0.28°C·h⁻¹; Tw_35.8, 0.80 ± 0.19°C·h⁻¹; Tw_37.2, 2.02 ± 0.31°C·h⁻¹; Tw_38.6, 3.54 ± 0.41°C·h⁻¹). Physically active divers risk severe hyperthermia in warmer waters. Increases in water temperature drastically increase the rate of core body temperature rise during work in warm water. New predictive models for core temperature based on workload and duration of warm water exposure are needed to ensure warm water diving safety.

Complete Genome Sequence of Geobacillus thermodenitrificans T12, A Potential Host for Biotechnological Applications

In attempt to obtain a thermophilic host for the conversion of lignocellulose derived substrates into lactic acid, Geobacillus thermodenitrificans T12 was isolated from a compost heap. It was selected from over 500 isolates as a genetically tractable hemicellulolytic lactic acid producer, requiring little nutrients. The strain is able to ferment glucose and xylose simultaneously and can produce lactic acid from xylan, making it a potential host for biotechnological applications. The genome of strain T12 consists of a 3.64 Mb chromosome and two plasmids of 59 and 56 kb. It has a total of 3.676 genes with an average genomic GC content of 48.7%. The T12 genome encodes a denitrification pathway, allowing for anaerobic respiration. The identity and localization of the responsible genes are similar to those of the denitrification pathways found in strain NG80-2. The hemicellulose utilization (HUS) locus was identified based on sequence homology against G. stearothermophilus T-6. It appeared that T12 has all the genes that are present in strain T-6 except for the arabinan degradation cluster. Instead, the HUS locus of strain T12 contains genes for both an inositol and a pectate degradation pathway. Strain T12 has complete pathways for the synthesis of purine and pyrimidine, all 20 amino acids and several vitamins except D-biotin. The host-defense systems present comprise a Type II and a Type III restriction-modification system, as well as a CRISPR-Cas Type II system. It is concluded that G. thermodenitrificans T12 is a potentially interesting candidate for industrial applications.

Hot springs of Indian Himalayas: potential sources of microbial diversity and thermostable hydrolytic enzymes

Microbial communities in hot springs at high elevations have been extensively studied worldwide. In this sense, the Indian Himalaya regions is valuable ecosystems for providing both the extreme 'cold' and 'hot' sites for exploring microbial diversity. In the present study, a total of 140 thermophilic bacteria were isolated from 12 samples collected from Manikaran and Yumthang hot springs of Indian Himalayas. The bacterial isolates were studied for phylogenetic profiling, growth properties at varying conditions and potential sources of extracellular thermostable hydrolytic enzymes such as protease, amylase, xylanase and cellulase. Based on production of extracellular hydrolases, 51 isolates from Manikaran (28) and Yumthang thermal springs (23) were selected and identified using 16S rRNA gene sequencing which included 37 distinct species of 14 different genera namely Anoxybacillus, Bacillus, Brevibacillus, Brevundimonas, Burkholderia, Geobacillus, Paenibacillus, Planococcus, Pseudomonas, Rhodanobacter, Thermoactinomyces, Thermobacillus, Thermonema and Thiobacillus. Out of 51 hydrolase producing bacteria, 24 isolates showed stability at wide range of temperature and pH treatments. In present investigation, three thermotolerant bacteria namely, Thermobacillus sp NBM6, Paenibacillus ehimensis NBM24 and Paenibacillus popilliae NBM68 were found to produced cellulase-free xylanase. These potential extracellular thermostable hydrolytic enzymes producing thermophilic bacteria have a great commercial prospect in various industrial, medical and agriculture applications.

Diversity of prokaryotic community at a shallow marine hydrothermal site elucidated by Illumina sequencing technology

To investigate the prokaryotic community structure and composition in an active hydrothermal site, named Black Point, off Panarea Island (Eolian Islands, Italy), we examined sediment and fluid samples, differing in temperature, by a massive parallel sequencing (Illumina) technique targeting the V3 region of the 16S rRNA gene. The used technique enabled us to detect a greater prokaryotic diversity than that until now observed and to reveal also microorganisms occurring at very low abundance (≤0.01 %). Most of sequences were assigned to Bacteria while Archaea were a minor component of the microbial community in both low- and high-temperature samples. Proteobacteria (mainly consisting of Alpha-, Gamma-, and Epsilonproteobacteria) dominated among all samples followed by Actinobacteria and Bacteroidetes. Analyzed DNA obtained from samples taken at different temperatures indicated the presence of members of different dominant genera. The main differences were observed between sediment samples where Rhodovulum and Thiohalospira prevailed at high temperature, while Thalassomonas and Sulfurimonas at low temperature. Chlorobium, Acinetobacter, Sulfurimonas, and Brevundimonas were abundant in both low- and high-temperature fluid samples. Euryarchaeota dominated the archaeal community in all samples. Classes of Euryarchaeota embracing hyperthermophilic members (Thermococci and Thermoplasmata) and of Crenarchaeota (Thermoprotei) were more abundant in high-temperature samples. A great number of sequences referred to Bacteria and Archaea still remained unaffiliated, indicating that Black Point site represents a rich source of so-far uncharted prokaryotic diversity.