Characterization of the gut microbiome in the beet armyworm Spodoptera exigua in response to the short-term thermal stress

The gut microbiota is critical for energy and nutrient utilization and plays a role in host immunity in response to environmental changes. The beet armyworm Spodoptera exigua is a worldwide polyphagous agricultural pest and has frequently experienced potentially stressful temperature fluctuations under natural environmental conditions. However, little is known about the effects of thermal stress on the gut microbiome of this moth pest. Therefore, we investigated the gut microbiome variations, composition and community structure of S. exigua among low-temperature (10 °C), control (26 °C) and high temperature (35 °C) treatments using 16S amplicon sequencing. Overall, 1,192,707 high-quality reads and 762 operational taxonomic units (OTUs) were detected from 15 samples. A total of 289 genera belonging to 19 bacterial phyla were captured, with Firmicutes and Proteobacteria being the most prominent phyla. Alpha diversity metrics indicated no significant differences in the gut bacterial diversity of S. exigua among the three temperature treatments. Principal coordinates and hierarchical cluster analysis revealed significant differences in the structure of gut microbiota between the low-temperature treatment and the other two temperature treatments. In addition, PICRUSt2 analysis demonstrated that the predicted metagenomes associated with the gut microbiome were amino carbohydrate transport and metabolism, acid transport and metabolism, inorganic ion transport and metabolism and cellular processes. Our study showed that thermal stress induced changes in the gut microbiome of the beet armyworm, which may contribute to better understanding the ecological adaptation of S. exigua under changing temperature trends and to evaluating the use of gut microorganisms as biocontrol agents for this pest.     

Effects of acute temperature changes on gut physiology in two species of sculpin from the west coast of Greenland

For a fish to thrive, the gut must function efficiently. This is achieved through a range of processes, including controlled patterns of gut motility and modifications in gut blood flow. The knowledge of how gut functions in fish are affected by environmental temperature is sparse, and in order to understand how changes in climate may affect fish populations, we need to understand how gut blood flow and gut motility are affected by changes in temperature. By simultaneous recording of gut blood flow, gut motility, cardiac output, heart rate and cardiac stroke volume, in vivo at 4, 9 and 14 °C, the acute thermal sensitivity of a thermal generalist (shorthorn sculpin Myoxocephalu scorpius) was compared to the more strictly Arctic species (Arctic sculpin M. scorpioides). Temperature effects on gut motility were further explored in vitro, using isolated smooth muscles. Elevated water temperatures increased gut blood flow and contractile activity. Contraction frequency increased nearly threefold and gut blood flow almost doubled with the 10 °C increase. Both cardiac output and heart rate increased with temperature, while cardiac stroke volume decreased. The cholinergic agonist carbachol was most potent on smooth muscles at 9 °C. There were no differences between the two species, suggesting that the gastrointestinal and cardiovascular systems of Arctic sculpin, although a more pronounced Arctic species, have similar abilities to cope with acute fluctuations in water temperature as shorthorn sculpin. The impact of increased gut activity at higher temperatures needs further investigation before the effects of climate change can be predicted.     

Development of a gut perfusion model as an alternative to the use of live fish

An alternative fish model with the principal aim of studying the interaction between fish pathogens and the intestinal tissue was developed. The preparation consisted of an excised gut tractus from rainbow trout (Oncorhynchus mykiss), perfused through cannulation of the aorta intestinalis ventralis with filtered and heparinized Cortland+dextran 1% as the perfusion fluid. This perfusion fluid was delivered by means of a drip. The perfused gut tractus was suspended in a circular bath filled with Ringer solution, which was aerated and kept at a constant temperature of 12 degrees C. Unperfused gut placed in Ringer solution at the same temperature served as the negative control. Perfusion was effective in maintaining the gut in a healthy condition for at least 60 min with only slight oedema and sloughing of the epithelium. Conversely, the unperfused gut revealed excessive tissue degeneration and severe necrosis.     

A comparison of the suitabilities of rectal,gut, and insulated axilla temperatures for measurement of the circadian rhythm of core temperature in field studies

Eight healthy males were studied for a total of 13 subject-days to assess if gut (from an ingested pill) and axilla (from a thermally insulated skin probe) temperatures would act as a substitute for rectal temperature in field studies of the circadian rhythm of core temperature. Subjects slept and went about their activities, indoors and outdoors, normally. Regular recordings (at 6min intervals) were made of temperatures from the three sites. In addition, activity was measured (by a sensor on the nondominant wrist) so that the raw temperature data could be “purified,” that is, corrected for the direct effects of sleep and activity. Inspection of the raw data indicated that there was a close parallelism between rectal and gut temperatures, but that the parallelism between rectal and insulated axilla temperatures was less reliable. This parallelism was supported by initial calculations of the correlations between rectal and gut temperatures (high and positive) and between rectal and insulated axilla (lower, though still positive) temperatures. Calculation of the limits of agreement between the parameters of the cosine curves fitted to the raw data confirmed that the rectal and gut temperatures were far closer with regard to acrophase and amplitude than were rectal and insulated axilla temperatures (-0.31±0.89 vs. +0.75±6.03 h and +0.002±0.116 vs. +0.083±0.625°C, respectively). After purification of the temperature data, the limits of agreement for the cosine parameters acrophase and amplitude still indicated that there was a closer agreement between rectal and gut temperatures than between rectal and insulated axilla temperatures (-0.30±1.12 vs. +0.58±6.69 h, and +0.007±0.116 vs. +0.104±0.620°C, respectively). Part of the explanation of this difference was the unreliable relationships between temperature changes in insulated axilla temperature and bursts of activity and going to bed. It is concluded that, whereas gut temperature is a viable alternative to rectal temperature (from the viewpoints of both user acceptability and the reliability of data obtained), insulated axilla temperature, though acceptable to subjects, is unreliable from an experimental viewpoint.     

A comparison of the suitabilities of rectal,gut, and insulated axilla temperatures for measurement of the circadian rhythm of core temperature in field studies

Eight healthy males were studied for a total of 13 subject-days to assess if gut (from an ingested pill) and axilla (from a thermally insulated skin probe) temperatures would act as a substitute for rectal temperature in field studies of the circadian rhythm of core temperature. Subjects slept and went about their activities, indoors and outdoors, normally. Regular recordings (at 6min intervals) were made of temperatures from the three sites. In addition, activity was measured (by a sensor on the nondominant wrist) so that the raw temperature data could be “purified,” that is, corrected for the direct effects of sleep and activity. Inspection of the raw data indicated that there was a close parallelism between rectal and gut temperatures, but that the parallelism between rectal and insulated axilla temperatures was less reliable. This parallelism was supported by initial calculations of the correlations between rectal and gut temperatures (high and positive) and between rectal and insulated axilla (lower, though still positive) temperatures. Calculation of the limits of agreement between the parameters of the cosine curves fitted to the raw data confirmed that the rectal and gut temperatures were far closer with regard to acrophase and amplitude than were rectal and insulated axilla temperatures (?0.31±0.89 vs. +0.75±6.03 h and +0.002±0.116 vs. +0.083±0.625°C, respectively). After purification of the temperature data, the limits of agreement for the cosine parameters acrophase and amplitude still indicated that there was a closer agreement between rectal and gut temperatures than between rectal and insulated axilla temperatures (?0.30±1.12 vs. +0.58±6.69 h, and +0.007±0.116 vs. +0.104±0.620°C, respectively). Part of the explanation of this difference was the unreliable relationships between temperature changes in insulated axilla temperature and bursts of activity and going to bed. It is concluded that, whereas gut temperature is a viable alternative to rectal temperature (from the viewpoints of both user acceptability and the reliability of data obtained), insulated axilla temperature, though acceptable to subjects, is unreliable from an experimental viewpoint.     

Temperature dependence of parasitic infection and gut bacterial communities in bumble bees

High temperatures (e.g., fever) and gut microbiota can both influence host resistance to infection. However, effects of temperature-driven changes in gut microbiota on resistance to parasites remain unexplored. We examined the temperature dependence of infection and gut bacterial communities in bumble bees infected with the trypanosomatid parasite Crithidia bombi. Infection intensity decreased by over 80% between 21 and 37°C. Temperatures of peak infection were lower than predicted based on parasite growth in vitro, consistent with mismatches in thermal performance curves of hosts, parasites and gut symbionts. Gut bacterial community size and composition exhibited slight but significant, non-linear, and taxon-specific responses to temperature. Abundance of total gut bacteria and of Orbaceae, both negatively correlated with infection in previous studies, were positively correlated with infection here. Prevalence of the bee pathogen-containing family Enterobacteriaceae declined with temperature, suggesting that high temperature may confer protection against diverse gut pathogens. Our results indicate that resistance to infection reflects not only the temperature dependence of host and parasite performance, but also temperature-dependent activity of gut bacteria. The thermal ecology of gut parasite-symbiont interactions may be broadly relevant to infectious disease, both in ectothermic organisms that inhabit changing climates, and in endotherms that exhibit fever-based immunity.     

Gut microbiota of invasive bullfrog tadpoles responds more rapidly to temperature than a noninvasive congener

Environmental temperature can alter the composition, diversity, and function of ectothermic vertebrate gut microbial communities, which may result in negative consequences for host physiology, or conversely, increase phenotypic plasticity and persistence in harsh conditions. The magnitude of either of these effects will depend on the length of time animals are exposed to extreme temperatures, and how quickly the composition and function of the gut microbiota can respond to temperature change. However, the temporal effects of temperature on gut microbiota are currently unknown. Here, we investigated the length of time required for increased temperature to alter the composition of gut bacterial communities in tadpoles of two frog species, the green frog, Lithobates clamitans, and its congener, the globally invasive American bullfrog, L. catesbeianus. We also explored the potential functional consequences of these changes by comparing predicted metagenomic profiles across temperature treatments at the last experimental time point. Bullfrog‐associated microbial communities were more plastic than those of the green frog. Specifically, bullfrog communities were altered by increased temperature within hours, while green frog communities took multiple days to exhibit significant changes. Further, over ten times more bullfrog bacterial functional pathways were temperature‐dependent compared to the green frog. These results support our hypothesis that bullfrog gut microbial communities would respond more rapidly to temperature change, potentially bolstering their ability to exploit novel environments. More broadly, we have revealed that even short‐term increases in environmental temperature, expected to occur frequently under global climate change, can alter the gut microbiota of ectothermic vertebrates.     

Seasonal change in the gastric evacuation rate of rainbow trout feeding on natural prey

Seasonal changes in the gastric evacuation rate ( R ) and gut contents of a wild population of rainbow trout Oncorhynchus mykiss feeding on natural prey at four water temperatures (2, 7, 9 and 12° C) were measured. The R and mass of the gut contents increased with water temperature, and prey items changed seasonally. These results suggest that the R of fish feeding on natural food depends primarily on water temperature, with their consumed prey being a secondary factor.     

Duration of gut passage and its dependence on temperature and food consumption in roach, Rutilus rutilus L: laboratory and field experiments

A laboratory method is described by means of which gut passage time as a function of temperature, diet and consumption rate is investigated in roach, an omnivorous cyprinid. Rates of food passage are accelerated by increasing temperature and food consumption. Equations for the regressions between gut passage time and consumption rate at four temperatures are given. Animal food causes a delay in gut passage time. In adult roach (30-100 g body weight) gut passage time was found to be independent of size.
A field method was also developed which allows the direct estimation of gut passage time and consumption rate in natural fish populations. The results of experiments with this field method agree with those of laboratory experiments.     

Effects of temperature on the food processing of three species of seaweed-eating fishes from European coastal waters

Food consumption, gut transit times and assimilation efficiencies of the temperate fishes Lipophrys pholis and Parablennius sanguinolentus (Blenniidae) and Gobius cobitis (Gobiidae. when fed the green alga Ulva lactuca were determined at four temperatures in the laboratory. Food consumption increased and gut transit times decreased with increase in temperature in all three species. Assimilation efficiencies for algal carbon and nitrogen did not vary with temperature in G. cobitis . Carbon but not nitrogen assimilation efficiency varied with temperature in P. sanguinolentus , and both carbon and nitrogen assimilation efficiencies changed broadly with temperature in L. pholis , the most omnivorous of the three fishes. Assimilation efficiencies of all three species were generally within the previously reported ranges for herbivorous marine fishes. These species are thus clearly capable of extracting energy from algal food sources.     

Ambient temperature alters body size and gut microbiota of Xenopus tropicalis

Temperature is important to determine physiological status of ectotherms. However, it is still not fully understood how amphibians and their symbiotic microbiota acclimate to ambient temperature. In this study, we investigated the changes of gut microbiota of Xenopus tropicalis at different temperatures under controlled laboratory conditions. The results showed that microbial communities were distinct and shared only a small overlap among froglet guts, culture water and food samples.Furthermore, the dominant taxa harbored in the gut exhibited low relative abundance in water and food. It indicates that bacterial taxa selected by amphibian gut were generally of low abundance in the external environment. Temperature could affect betadiversity of gut microbiota in terms of phylogenetic distance, but it did not affect alpha diversity. The composition of gut microbiota was similar in warm and cool treatments. However, signature taxa in different temperature environments were identified. The relationships between temperature, gut microbiota and morphology traits of X. tropicalis revealed in this study help us to predict the consequences of environmental changes on ectothermic animals.     

Environmental filtering increases with elevation for the assembly of gut microbiota in wild pikas

Despite their important roles in host nutrition, metabolism and adaptability, the knowledge on how the mammalian gut microbial community assemble is relatively scanty, especially regarding the ecological mechanisms that govern microbiota along environmental gradients. To address this, we surveyed the diversity, function and ecological processes of gut microbiota in the wild plateau pika, Ochotona curzoniae, along the elevational gradient from 3106 to 4331 m on ‘the Roof of the World’—Qinghai-Tibet Plateau. The results indicated that the alpha, beta and functional diversity of gut microbiota significantly increased with elevation, and elevation significantly explained the variations in the gut microbial communities, even after controlling for geographical distance, host sex and body weight. Some gene functions (e.g. nitrogen metabolism and protein kinases) associated with metabolism were enriched in the high-altitude pikas. Null model and phylogenetic analysis suggest that the relative contributions of environmental filtering responsible for local gut communities increased with elevation. In addition, deterministic processes dominated gut microbial communities in the high-altitude (more than 3694 m) pikas, while the percentages of stochastic and deterministic processes were very close in the low-altitude (3106 and 3580 m) pikas. The observed mechanisms that influence pika gut microbiota assembly and function seemed to be mainly mediated by the internal gut environment and by the external environmental pressure (i.e. lower temperature) in the harsh high-altitude environment. These findings enhance our understanding of gut microbiota assembly patterns and function in wild mammals from extreme harsh environments.     

Predator gut state and prey detectability using electrophoretic analysis of gut contents

Abstract. I. An investigation of the effects of position of food in the gut (gut state), time since feeding, meal size and environmental temperature on the detection of prey using the electrophoretic separation of proteins with esterase activity was undertaken. The waterbug Notonecta glauca Linn (Hemiptera/Heteroptera) was used as the model predator.
2. Seven easily recognizable gut states can be identified at different times since commencement of a meal.
3. Specific prey esterase 'fingerprint' bands can be detected whilst food remains in the foregut.
4. Meal size and environmental temperature (affecting digestion and assimilation rates) both affect the rate of filling and emptying of the foregut, and hence the time period over which prey proteins can be detected by electrophoresis following a meal. Small meals and high temperatures lead to quite rapid changes in gut state with time and thus reduce the time period over which prey can be identified from gut contents (20 h). Large meals and low temperatures extend this period (48 h).
5. Predator gut state is the most important parameter in prey detectability from gut contents, and from a visual examination of the gut state it is immediately evident whether or not prey detection by electrophoresis will be possible.
6. There is further evidence in support of a twocompartment food processing model for Nofoonecru , and the significance of this type of processing in relation to gut content analysis of sucking predators is discussed.     

Seasonal change in the gut clearance rate of three stonefly species in a Japanese stream

We measured seasonal changes in the gut clearance rate of three stonefly species in a stream. The rate declined with water temperature. Based on the gut clearance rate obtained here, we estimated the half-reduction time of gut contents and consumption rate of stoneflies on algae. Irrespective of stonefly species, the half-reduction time in winter (2 days) was twice as long as that in summer (1 day). The areal consumption rates of stoneflies varied depending on species and season. These results imply that the seasonal consumption impact of aquatic insects can be different, despite their daily ration being similar among species.     

Feeding chronology,daily ration,and the effects of temperature upon gastric evacuation in the pipefish,Syngnathus fuscus

Synopsis Feeding chronology, daily ration, and the effects of temperature upon gastric evacuation were examined in the pipefish,Syngnathus fuscus, from field and laboratory data.S. fuscus displayed a pattern of diurnal feeding, characteristic of syngnathids. Daily ration calculations yielded estimates of 4.0 and 4.4% body weight per day, which are comparable to estimates for other teleosts. Evacuation rate was found to be temperature dependent. with more rapid evacuation with increasing temperature. In addition, evacuation rate was found to be positively correlated with gut content. Slowing of evacuation rate with decreasing gut content may allow for increased assimilation efficiency during periods of low food availability. Daily ration, although controlled by the temperature dependence of evacuation rate, may also be controlled by prey abundance; fish maximize food intake during periods of high prey availability, and maximize upon assimilation during periods of low prey availability.Contribution number 1035 of the Virginia Institute of Marine Science of the College of William and Mary.     

Climate change is not just global warming: Multidimensional impacts on animal gut microbiota

Climate change has rapidly altered many ecosystems, with detrimental effects for biodiversity across the globe. In recent years, it has become increasingly apparent that the microorganisms that live in and on animals can substantially affect host health and physiology, and the structure and function of these microbial communities can be highly sensitive to environmental variables. To date, most studies have focused on the effects of increasing mean temperature on gut microbiota, yet other aspects of climate are also shifting, including temperature variation, seasonal dynamics, precipitation and the frequency of severe weather events. This array of environmental pressures might interact in complex and non-intuitive ways to impact gut microbiota and consequently alter animal fitness. Therefore, understanding the impacts of climate change on animals requires a consideration of multiple types of environmental stressors and their interactive effects on gut microbiota. Here, we present an overview of some of the major findings in research on climatic effects on microbial communities in the animal gut. Although ample evidence has now accumulated that shifts in mean temperature can have important effects on gut microbiota and their hosts, much less work has been conducted on the effects of other climatic variables and their interactions. We provide recommendations for additional research needed to mechanistically link climate change with shifts in animal gut microbiota and host fitness.     

Cold hardiness of the overwintering black carpenter ant

Abstract Cold hardiness was investigated in overwintering field nests of the black carpenter ant Camponotus pennsylvanicus (De Geer) in the Commonwealth of Virginia. No active nest thermoregulation was observed: temperatures of galleries, worker bodies, worker clusters, and larval clusters were within 3°C of ambient temperature. Nest temperatures generally fluctuated less rapidly and severely than did ambient temperature; thus, the nest afforded protection from potentially fatal sudden temperature drops. Glycerol, the only polyol cryoprotectant detected, was found in all castes and larvae. Supercooling points were low and ranged from ? 17°C in major workers to ?22°C in larvae. A second heat release peak, occurring around ? 8°C, was seen in all adults, but it was not observed in larvae. This higher temperature peak in adults probably represents the freezing of the gut contents, as adults were found to overwinter with the crop full or partially full. Larvae did not overwinter with liquid food in the gut.     

Amylase activity in the alimentary tract and salivary glands of Periplaneta americana L

The optimum conditions for amylase activity and the distribution of the enzyme in the salivary glands and various gut regions were investigated. Maximum activity of the enzyme was observed at 7.0 pH and 50 degrees C temperature and the activity increased with increasing time period, and enzyme and substrate concentrations. Amylase from the salivary glands was found to be exceptionally potent and the enzyme concentration decreased from the anterior to the posterior part of the gut in well-fed cockroaches. The findings are discussed with regard to the source of amylase synthesis.     

Field estimates of feeding rate for Gammarus pseudolimnaeus (Crustacea: Amphipoda) in the Credit River, Ontario

SUMMARY. The feeding rate of G. pseudolimnaeus was measured monthly for 7 months in the field by monitoring the decline in weight of gut contents when the amphipod was starved. This decline was modelled by an exponential regression of weight on time. As the amphipods appeared to be continuous feeders, feeding rate was calculated by multiplying the dry weight of a full gut by the specific rate of emptying, i.e., the slope of the exponential regression. Specific rate of emptying was independent of animal size, but increased with temperature. Therefore, food has a longer period in which to be digested at low temperatures, which suggests that assimilation efficiency may increase.
However, the assimilation efficiency of amphipods feeding on decaying maple leaves in the laboratory was only 10% and did not vary with temperature. Ingestion and egestion rates were measured in the laboratory by weighing amounts eaten and defecated. The turnover time of the contents of a full gut in the laboratory often agreed very well with turnover time measured in the field, i.e., the reciprocal of the specific rate of emptying, thus confirming the use of an exponential regression.     

家蚕肠道枯草杆菌产蛋白酶的发酵条件与酶学性质

肠道微生物分泌的蛋白酶可促进家蚕对桑叶养分的消化吸收,枯草芽孢杆菌是家蚕肠道内一种重要的产蛋白酶菌株。为提高枯草芽孢杆菌蛋白酶的高效利用,对该菌株适宜发酵条件及酶学性质进行了研究。结果表明：各因素对枯草芽孢杆菌产酶活性影响的大小顺序依次为：pH值〉培养温度〉培养时间〉装液量;最适的产酶条件为：pH=7,培养温度：30 ℃,培养时间：36 h;对枯草芽孢杆菌产蛋白酶进行初步提纯后并研究得出该酶反应的最适pH 10.0,最适反应温度为：60 ℃;该酶为碱性蛋白酶、不耐高温、不耐酸,但在35 ℃条件下热稳定性较好。