Endolithic microbial life in hot and cold deserts

Endolithic microorganisms (those living inside rocks) occur in hot and cold deserts and exist under extreme environmental conditions. These conditions are discussed on a comparative basis. Quantitative estimates of biomass are comparable in hot and cold deserts. Despite the obvious differences between the hot and cold desert environment, survival strategies show some common features. These endolithic organisms are able to switch rapidly their metabolic activities on an off in response to changes in the environment. Conditions in hot deserts impose a more severe environmental stress on the organisms than in the cold Antarctic desert. This is reflected in the composition of the microbial flora which in hot desert rocks consist entirely of prokaryotic microorganisms, while under cold desert conditions eukaryotes predominate.Proceedings of the Fourth College Park Colloquium on Chemical Evolution:Limits of Life, University of Maryland, College Park, 18–20 October 1978.     

Metagenomic insights into the fungal assemblages of the northwest Himalayan cold desert

Psychrophilic fungi are a critical biotic component in cold deserts that serves a central role in nutrient recycling and biogeochemical cycles. Despite their ecological significance, culture-independent studies on psychrophilic mycobiome are limited. In the present study, the fungal diversity patterns across the Drass, an Indian cold desert in the Himalaya, were indexed by targeted amplicon pyrosequencing (ITS). In the Drass dataset, Ascomycota was represented by 92 genera, while 22 genera represented Basidiomycota. The most abundant genus was Conocybe (20.46%). Most of the identified genera were reported in the literature to be prolific extracellular hydrolytic enzyme producers. To identify whether the Drass fungal assemblages share similarities to other cold deserts, these were further compared to Antarctic and Arctic cold deserts. Comparative analysis across the three cold deserts indicated the dominance of Dikarya (Ascomycota and Basidiomycota). The observed alpha diversity, Shannon index as well as Pielou's evenness was highest in the Antarctic followed by Drass and Arctic datasets. The genera Malassezia, Preussia, Pseudogymnoascus, Cadophora, Geopora, Monodictys, Tetracladium, Titaea, Mortierella, and Cladosporium were common to all the cold deserts. Furthermore, Conocybe was represented predominantly in Drass. Interestingly, the genus Conocybe has not been previously reported from any other studies on Antarctic or Arctic biomes. To the best of our knowledge, this is the first fungal metagenome study in Drass soil. Our analysis shows that despite the similarities of low temperature among the cold deserts, a significant differential abundance of fungal communities prevails in the global cold deserts.

     

Testing the monophyly and position of the North American shrubby desert genus Leucophyllum (Scrophulariaceae: Leucophylleae)

Leucophyllum is one of the most remarkable endemic genera of North American deserts, with its simultaneous bloom of showy purple flowers. With Eremogeton and probably Capraria it forms part of tribe Leucophylleae. Leucophyllum has 16 species distributed mostly throughout the Chihuahuan and Tehuacán deserts. The three genera were sampled to investigate the phylogenetic relationships among them and to test the monophyly of Leucophyllum, based on plastid DNA (trnL‐F, rps16) and nuclear ribosomal (nr)DNA (internal transcribed spacer) sequences. Bayesian inference and maximum‐likelihood analyses confirmed that tribe Leucophylleae is monophyletic and formed by the three Neotropical genera. Separate (plastid DNA and nrDNA) and combined analyses retrieved Leucophyllum as paraphyletic, with L. mojinense as the sister species to the rest of the species in the tribe and Capraria spp. nested in one of two clades of Leucophyllum. Further monographic work is needed to identify the defining characters and limits of the genera, but we suggest that L. mojinense, with its different vegetative architecture, distinctive flowers and dissimilar distribution could be placed in its own genus. Each of the two clades in Leucophyllum could be considered a genus in its own right, and Capraria and Eremogeton can be recognized as independent genera, as they are at present. Leucophyllum ambiguum, the type species of the genus, belongs to one of the clades so the species of the other could be considered members of a new genus. The only diagnostic character detected at present is a ventricose corolla tube in one of the clades in Leucophyllum and a pressed corolla tube in the other. © 2013 The Linnean Society of London     

Stem tilting in the inter‐tropical cactus Echinocactus platyacanthus: an adaptive solution to the trade‐off between radiation acquisition and temperature control

While plants require radiation for photosynthesis, radiation in warm deserts can have detrimental effects from high temperatures. This dilemma may be solved through plant morphological attributes. In cold deserts, stem tilting keeps reproductive organs warm by increasing radiation interception at the cost of decreased annual light interception. Conversely, little is known about stem tilting in warm deserts. We hypothesised that stem tilting in Echinocactus platyacanthus prevents high temperatures near the apex, where reproduction occurs. The study was conducted in the warm, inter‐tropical portion of the Chihuahuan Desert, Mexico. We found that cacti preferentially tilted towards the south, which reduced temperatures of reproductive organs during the hot season, but increased total annual near‐apex PAR interception. Tilting also maximised reproduction, a likely consequence of temperature control but perhaps also of the difficulty in translocating photosynthates in cacti; therefore, annual energy acquisition near floral meristems may be largely allocated to reproduction. Unlike plants of higher latitudes, in inter‐tropical deserts sunlight at noon comes either from the north or the south, depending on the season, and thus stem tilting may more strongly affect total annual radiation received in different portions of the stem. Inter‐tropical cacti can synchronise reproduction with irradiance peaks if flowering occurs in a specific (north or south) portion of the stem; also, they effectively solve the conflict between maximising annual PAR interception and minimising temperature at the hottest time of day. Notably, the two inter‐tropical cacti in which stem tilting has been studied successfully solve this conflict.     

Identifying Pleistocene refugia in North American cold deserts using phylogeographic analyses and ecological niche modelling

Aim We analysed phylogeographic patterns and ecological niche models (ENMs) of the widespread velvet ant (Hymenoptera: Mutillidae) Sphaeorpthalma difficilis to understand the history of diversification in the Nearctic deserts and to identify areas that may have been cold‐desert refugia during the Pleistocene. These areas should be targeted for conservation because of their climatic stability throughout historical climate change events. Location North American arid regions. Methods The two internal transcribed spacer regions (ITS1 and ITS2) were sequenced and analysed using Bayesian techniques to uncover phylogeographic patterns of relatedness among S. difficilis populations. History of diversification was estimated using parsimony‐based and maximum likelihood character reconstructions. Molecular dating analyses were implemented in the program r8s and were calibrated with Dominican amber fossils. ENMs were developed based on current climate data and projected onto Pleistocene climate surfaces. Results The analyses suggest that S. difficilis had a complex history of Pleistocene range expansion and contraction that led to the formation of genetically distinct populations inhabiting distinct arid regions. ENMs and phylogeographic patterns indicate that several cold‐desert refugia existed in North America, particularly in the Colorado Plateau and parts of the Great Basin Desert. Main conclusions Analyses of S. difficilis are used to identify potential Pleistocene refugia in the North American cold deserts. Because these areas represent climatically stable locations, they are critical for the long‐term persistence of biodiversity. This research provides evidence that in addition to desert‐like conditions persisting through the ice age in parts of the Nearctic warm deserts, many areas maintained desert‐like characteristics in the regional cold deserts. Further work is needed to elucidate options for preserving biodiversity in these cold‐desert refugia.     

Immunoblot Analysis of Exospore Polypeptides from Some Entomophilic Microsporidia12

ABSTRACT. Immunological relationships between genera and species of microsporidia were examined by immunoblot analysis. Exospore polypeptides from two Nosema spp., three Vairimorpha spp., and two undescribed Vairimorpha-like isolates were analyzed. Gel electrophoresis and immunoblot analysis revealed that a variety of polypeptides, mostly between 15,000 and 90,000 molecular weight, are present on the exospore. The three Vairimorpha spp. are closely related immunologically to each other, but less so to the two undescribed Vairimorpha-like isolates. The two Nosema spp. are immunologically distant from each other and from the Vairimorpha spp. Indirect evidence, however, indicated that many internal spore polypeptides present in both genera are similar. Cross-reactivity between exospore polypeptides from entomophilic microsporidia and antisera to a mammalian microsporidium, Encephalitozoon cuniculi, was very limited. These results indicate that immunoblot analysis of exospore polypeptides may be employed to investigate the interrelatedness of microsporidian species, and that exospore polypeptides of some microsporidia are sufficiently diverse to be of immunodiagnostic value.     

Exploring levels of egg parasitism and variation in egg cuticular chemistry in different Clavigralla spp.

Clavigralla spp. (Hemiptera: Coreidae) are major pests of cowpea (Vigna unguiculata (L.) Walp, Fabacae), common bean (Phaseolus vulgaris L., Fabacae) and pigeon pea (Cajanus cajan L., Fabacae) in Africa. Clavigralla spp. egg parasitoids, Gryon spp. (Hymenoptera: Scelionidae), have previously been reported as potential biological control candidates. Little is known about the parasitism levels and their potential relationship with cuticular chemistry of Clavigralla spp. The aims of this study were to determine parasitism levels of Clavigralla tomentosicollis Stål (Hemiptera: Coreidae) and C. elongata Signoret (Hemiptera: Coreidae) eggs, and to explore the relationship between egg parasitism and egg cuticular chemistry. High parasitism levels were determined for C. tomentosicollis by collecting eggs from plants in mono‐cropping and multi‐cropping systems in farmers’ fields in Bénin and Kenya between April and June 2016. Three species of Clavigralla were recorded: C. tomentosicollis, C. shadabi and C. elongata. Clavigralla tomentosicollis was the most common in both countries, while C. shadabi and C. elongata were only collected in Bénin and Kenya, respectively. An egg parasitoid (Gryon sp.) was recovered from egg batches collected from both countries. In parasitism assays using Gryon sp., the incidence of parasitism was higher in C. tomentosicollis eggs than that of C. elongata. Chemical analysis by coupled gas chromatography/mass spectrometry (GC/MS) of cuticular extracts obtained from C. tomentosicollis and C. elongata eggs identified fifteen compounds including ten alkanes of which the amounts varied between the two species. We speculate that Clavigralla spp. cuticular chemistry may serve as potential host location cues for Gryon sp.     

Variation of cuticular characters in the Nematomorpha: studies on Gordionus violaceus (Baird, 1853) and G. wolterstorffii (Camerano, 1888) from Britain and Ireland

Gordionus violaceus (Baird, 1853) and G. wolterstorffii (Camerano, 1888) are regarded as two species which are clearly separated by distinct cuticular patterns. A study of 59 specimens of these two species from Britain and Ireland revealed numerous transitional stages between the cuticular patterns that are regarded as being typical for each species. Variation was also found at the posterior end, but no character separates both species. Therefore, G. violaceus and G. wolterstorffii might represent one polymorphic species. Four specimens resembled G. violaceus but had a different cuticular pattern, including a second type of areole occurring in a pattern which has been named a megareolar pattern. This might represent a separate species, but a detailed determination relies upon further revisional work in the genera Gordionus, Parachordodes and Paragordionus.     

It’s a wormy world: Meta‐analysis reveals several decades of change in the global abundance of the parasitic nematodes Anisakis spp. and Pseudoterranova spp. in marine fishes and invertebrates

The Anthropocene has brought substantial change to ocean ecosystems, but whether this age will bring more or less marine disease is unknown. In recent years, the accelerating tempo of epizootic and zoonotic disease events has made it seem as if disease is on the rise. Is this apparent increase in disease due to increased observation and sampling effort, or to an actual rise in the abundance of parasites and pathogens? We examined the literature to track long‐term change in the abundance of two parasitic nematode genera with zoonotic potential: Anisakis spp. and Pseudoterranova spp. These anisakid nematodes cause the disease anisakidosis and are transmitted to humans in undercooked and raw marine seafood. A total of 123 papers published between 1967 and 2017 met our criteria for inclusion, from which we extracted 755 host–parasite–location–year combinations. Of these, 69.7% concerned Anisakis spp. and 30.3% focused on Pseudoterranova spp. Meta‐regression revealed an increase in Anisakis spp. abundance (average number of worms/fish) over a 53 year period from 1962 to 2015 and no significant change in Pseudoterranova spp. abundance over a 37 year period from 1978 to 2015. Standardizing changes to the period of 1978–2015, so that results are comparable between genera, we detected a significant 283‐fold increase in Anisakis spp. abundance and no change in the abundance of Pseudoterranova spp. This increase in Anisakis spp. abundance may have implications for human health, marine mammal health, and fisheries profitability.     

INVESTIGATIONS OF ANGIOSPERMS FROM THE EOCENE OF NORTH AMERICA: STIPULATE LEAVES OF THE RUBIACEAE INCLUDING A PROBABLE POLYPLOID POPULATION

A comparative study was made of the gross morphology, fine venation and cuticular features of Leitneria fioridana Chapman, the single living representative of the order Leitneriales and Leitneria eocenica (Berry) Brown, presumbaly a related fossil species. In addition to the type material, newly collected fossil specimens were investigated from clay pits in the Middle Eocene, Claiborne Formation, of western Tennessee and Kentucky. Foliate stipules attached to the petioles of several specimens suggest the assignment of this fossil leaf type to the genus Leitneria is incorrect. The nature of the gross morphology, fine venation and cuticular features confirms the misidentification. Previously, various specimens of this fossil leaf type have been placed in eight species of seven genera in seven families of six angiosperm orders, none of which are correct systematically. The gross morphology, venation and cuticular characters of the fossil leaf are distributed among a few extant South American genera of arborescent Rubiaceae. The fossil is an extinct rubiaceous leaf type which cannot be placed within a single modern subfamily, tribe or genus of the family. The organ genus, Paleorubiaceophyllum is proposed for these leaves. Three varieties of a single fossil species, P. eocenicum, are recognized. One variety with epidermal cells nearly twice the size of the others may represent a polyploid population.     

Cold active pectinase,amylase and protease production by yeast isolates obtained from environmental samples

The present study was performed to screen for psychrophilic yeasts that are able to secrete cold active enzymes. Yeast isolates were obtained from environmental samples from northern Turkey and examined for enzyme production at low temperatures. The isolates which were capable of cold active enzyme production on plates were identified by molecular identification techniques. It has been found that the isolates belonged to three genera of yeasts, i.e., Rhodosporidiobolus, Cystofilobasidium and Yamadazyma. The isolates were then fermented in different media at 15 °C and the pectinase, amylase and protease activities were determined in the range of 0.76–1.73, 0.5–1.57 and 2.11–10.53 U/mL, respectively. Maximum enzyme activities were found in Yamadazyma isolates for all three enzymes. To the best of our knowledge, cold active pectinase, amylase and protease production by Yamadazyma spp. were investigated for the first time in the present study. Besides, this is the first report which indicates cold active amylase production by Cystofilobasidium capitatum and pectinase production by Rhodosporidiobolus colostri. Yeast isolates obtained in this study may have potential for industrial cold active enzyme production.

     

Isolation of root-associated Pseudomonas and Burkholderia spp. with biocontrol and plant growth-promoting traits

Novel, root-associated Pseudomonas and Burkholderia strains with biological control and plant growth-promoting (PGP) traits are being sought for biotechnological application in agriculture. We present a new isolation approach for recovery of rhizoplane and/or endophytic Pseudomonas and Burkholderia spp. with desirable biocontrol and PGP phenotypes. The method may enable better targeted biodiscovery of these two important genera.     

Succession of microfungal flora on Rodgersia podophylla plants at the forest side of Cryptomeria plantation

Microfungal flora on aerial parts of a forest floor plant, Rodgersia podophylla, were studied at the forest side of a Japanese cedar plantation. From May to October, Nigrospora spp. were dominantly isolated from leaves, whereas Acremonium spp. and Fusarium spp. were dominant on stems, suggesting that the aerial part of the plants about 1 m height can offer two different habitats for these dominant fungi. In September and October, we could easily discern different types of tissue on the withering leaves, i.e., brown (necrotic lesion), yellowish (border tissue between brown and green areas), and green (healthy tissue). Nigrospora spp. and Pestalotiopsis spp. were continuously isolated on the brown area as well as on green and yellowish areas. Pathogenicity of N. sacchari and P. neglecta on potted plant leaves was confirmed by inoculation. From these, the fungi of these two genera seemed to have changed from quiescent to pathogenic with leaf senescence. Sporulations by fungi of the two genera were recognized on overwintered stems. These fungi may overwinter in stems that are slow to decompose, and seem to go over to the leaves in the following spring. Thus, they could be candidates for parasites that may play an important role in decomposition of the plant.     

The use of wild edible plants in western and central Anatolia (Turkey)

In this study, 121 wild edible plants used as food in Anatolia were surveyed to determine the plant parts used and their detailed preparation methods. The results of this study show that the plants may be boiled, fried in fat, and eaten raw or as rolled vegetables. They may also be consumed as pickles, fruits, sweets and spices, and drunk as cold and hot drinks. Thirty species (8 genera) were identified as belonging to the Lamiaceae family, 15 species (15 genera) belong to the Asteraceae family, 13 species (5 genera) belong to the Rosaceae family, 8 species (7 genera) belong to the Brassicaceae family, 6 species (3 genera) belong to the Orchidaceae family and 5 species (5 genera) belong to the Apiaceae family. The genera represented by the highest number of species in the study are as follows:Sideritis L. is represented by 13 species, Origanum L. by 7 species,Rubus L. by 5 species,Thymus L. by 4 species andRumex L. by 4 species.     

Bacterial Community Structure Along Moisture Gradients in the Parafluvial Sediments of Two Ephemeral Desert Streams

Microorganisms inhabiting stream sediments mediate biogeochemical processes of importance to both aquatic and terrestrial ecosystems. In deserts, the lateral margins of ephemeral stream channels (parafluvial sediments) are dried and rewetted, creating periodically wet conditions that typically enhance microbial activity. However, the influence of water content on microbial community composition and diversity in desert stream sediments is unclear. We sampled stream margins along gradients of wet to dry sediments, measuring geochemistry and bacterial 16S rRNA gene composition, at streams in both a cold (McMurdo Dry Valleys, Antarctica) and hot (Chihuahuan Desert, New Mexico, USA) desert. Across the gradients, sediment water content spanned a wide range (1.6–37.9% w/w), and conductivity was highly variable (12.3–1,380 μS cm⁻²). Bacterial diversity (at 97% sequence similarity) was high and variable, but did not differ significantly between the hot and cold desert and was not correlated with sediment water content. Instead, conductivity was most strongly related to diversity. Water content was strongly related to bacterial 16S rRNA gene community composition, though samples were distributed in wet and dry clusters rather than as assemblages shifting along a gradient. Phylogenetic analyses showed that many taxa from wet sediments at the hot and cold desert site were related to, respectively, halotolerant Gammaproteobacteria, and one family within the Sphingobacteriales (Bacteroidetes), while dry sediments at both sites contained a high proportion of taxa related to the Acidobacteria. These results suggest that bacterial diversity and composition in desert stream sediments is more strongly affected by hydrology and conductivity than temperature.     

Too hot to die? The effects of vegetation shading on past,present, and future activity budgets of two diurnal skinks from arid Australia

Behavioral thermoregulation is an important mechanism allowing ectotherms to respond to thermal variations. Its efficiency might become imperative for securing activity budgets under future climate change. For diurnal lizards, thermal microhabitat variability appears to be of high importance, especially in hot deserts where vegetation is highly scattered and sensitive to climatic fluctuations. We investigated the effects of a shading gradient from vegetation on body temperatures and activity timing for two diurnal, terrestrial desert lizards, Ctenotus regius, and Morethia boulengeri, and analyzed their changes under past, present, and future climatic conditions. Both species’ body temperatures and activity timing strongly depended on the shading gradient provided by vegetation heterogeneity. At high temperatures, shaded locations provided cooling temperatures and increased diurnal activity. Conversely, bushes also buffered cold temperature by saving heat. According to future climate change scenarios, cooler microhabitats might become beneficial to warm‐adapted species, such as C. regius, by increasing the duration of daily activity. Contrarily, warmer microhabitats might become unsuitable for less warm‐adapted species such as M. boulengeri for which midsummers might result in a complete restriction of activity irrespective of vegetation. However, total annual activity would still increase provided that individuals would be able to shift their seasonal timing towards spring and autumn. Overall, we highlight the critical importance of thermoregulatory behavior to buffer temperatures and its dependence on vegetation heterogeneity. Whereas studies often neglect ecological processes when anticipating species’ responses to future climate change the strongest impact of a changing climate on terrestrial ectotherms in hot deserts is likely to be the loss of shaded microhabitats rather than the rise in temperature itself. We argue that conservation strategies aiming at addressing future climate changes should focus more on the cascading effects of vegetation rather than on shifts of species distributions predicted solely by climatic envelopes.     

Assessment of Microbial Diversity in Saudi Springs by Culture-Dependent and Culture-Independent Methods

Culture-dependent and culture-independent methods were used to evaluate the microbial diversity in two hot springs of the Aljouf region in Saudi Arabia, including Qasr Kaff and Ain Hawas. Physicochemical characteristics of the springs were examined to establish their effect on the biodiversity of thermophilic bacteria and fungi. We employed culture-dependent techniques to study microbial diversity using four different complex media for bacteria and fungi. In addition, the direct count for algal populations from two springs was investigated. We surveyed the microbial diversity in water and sediment samples from both springs by denaturing gradient gel electrophoresis (DGGE) and clone library construction. Bacillariophycaea (18 species) was the most diverse group, followed by Cyanophyceaea. Bacterial isolates closer to the genera Bacillus spp., Geobacillus, Thermoactinomyces, and unidentified actinobacteria were recovered. Fungal isolates were related to Aspergillus, Pezizaceae, Penicillium, Acremonium, Fusarium, Chrysosporium, and Stachybotrys. Using molecular-based techniques, the results were slightly different from those obtained by culture-dependent methods, and more genera were obtained. However, most genera were uncultured microbes, particularly from bacterial communities.     

Phylogenetic relationships between the slave‐making ants Rossomyrmex and their Proformica hosts in relation to other genera of the ant tribe Formicini (Hymenoptera: Formicidae)

The ant genus Proformica is very common to Eurasian semi‐deserts, and a few species are parasitized by the slave‐making ants Rossomyrmex. However, the phylogenetic relationship between Proformica (host) and Rossomyrmex (parasite) remains unclear as another closely related genus (Cataglyphis) could be a sister group of Rossomyrmex. This work has two main goals: (i) to study the phylogenetic relationships among Proformica, Rossomyrmex, and other genera of the tribe Formicini, with a special focus on the highly diverse genus Cataglyphis; and (ii) to reconstruct the biogeographical distribution of parasite and host genera. We perform a phylogenetic study for the first time including several species of the genera Rossomyrmex, Proformica, and Cataglyphis. Our results indicate that Proformica and Rossomyrmex are reciprocally monophyletic and that Rossomyrmex is nested within Cataglyphis, rendering the latter paraphyletic. Finally, the ancestral distribution range of the host genus could be situated in Central Asia and subsequently dispersed to Western Europe, whereas additional studies are required to clarify the range of the parasite.