Unraveling the cellulolytic and hemicellulolytic potential of two novel <Emphasis Type="Italic">Streptomyces</Emphasis> strains

The Streptomyces spp. are notorious plant biomass decomposers in soil environments, but only few strains were biochemically and genetically characterized. Here, we employed functional screening along with genomic sequencing for identification of novel lignocellulolytic Streptomyces strains. Streptomyces strains isolated from soil were functional screened based on their cellulolytic and hemicellulolytic capacities by enzymatic plate assays containing carboxymethylcellulose (CMC) and beechwood xylan as sole carbon source. Subsequently, genomes of Streptomyces strains were sequenced, annotated, and interpreted to correlate their genetic contents with biochemical properties. Among the 80 bacterial isolates that were screened for enzymatic activity, two Streptomyces strains (named as F1 and F7) exhiting higher endoglucanase and endoxylanase activities were selected for biochemical and genomic characterization. After cultivation on steam-pretreated sugarcane bagasse-based medium, the supernatant of the strains F1 and F7 exhibited enzymatic activity against different substrates, such as arabinan, rye arabinoxylan, β-glucan, starch, CMC, xylan, and chitin. Furthermore, strain F7 was able to degrade pectin, mannan, and lichenan. The genomic analysis of both strains revealed a diversity of carbohydrate-active enzymes. The F1 and F7 genomes encode 33 and 44 different types of glycosyl hydrolases families, respectively. Moreover, the genomic analysis also identified genes related to degradation of lignin-derived aromatic compounds. Collectively, the study revealed two novel Streptomyces strains and further insights on the degradation capability of lignocellulolytic bacteria, from which a number of technologies can arise, such as saccharification processes.     

Surviving in hot and cold: psychrophiles and thermophiles from Deception Island volcano,Antarctica

Extremophiles - Polar volcanoes harbor unique conditions of extreme temperature gradients capable of selecting different types of extremophiles. Deception Island is a marine stratovolcano located...     

Land use legacy effects on woody vegetation in agricultural landscapes of south‐western Ethiopia

Aim

Past land use legacy effects—extinction debts and immigration credits—might be particularly pronounced in regions characterized by complex and dynamic landscape change. The aim of this study was to evaluate how current woody plant species distribution, composition and richness related to historical and present land uses.

Location

A smallholder farming landscape in south‐western Ethiopia.

Methods

We surveyed woody plants in 72 randomly selected 1‐ha sites in farmland and grouped them into forest specialist, generalist and pioneer species. First, we investigated woody plant composition and distribution using non‐metric multidimensional scaling. Second, we modelled species richness in response to historical and current distance from the forest edge. Third, we examined diameter class distributions of trees in recently converted vs. permanent farmland.

Results

Historical distance was a primary driver of woody plant composition and distribution. Generalist and pioneer species richness increased with historical distance. Forest specialists, however, did not respond to historical distance. Only few old individuals of forest specialist species remained in both recently converted and permanent farmlands.

Main conclusions

Our findings suggest that any possible extinction debt for forest specialist species in farmland at the landscape scale was rapidly paid off, possibly because farmers cleared large remnant trees. In contrast, we found substantial evidence of immigration credits in farmland for generalist and pioneer species. This suggests that long‐established farmland may have unrecognized conservation values, although apparently not for forest specialist species. We suggest that conservation policies in south‐western Ethiopia should recognize not only forests, but also the complementary value of the agricultural mosaic—similar to the case of European cultural landscapes. A possible future priority could be to better reintegrate forest species in the farmland mosaic.

     

Genomic prediction applied to high-biomass sorghum for bioenergy production

The increasing cost of energy and finite oil and gas reserves have created a need to develop alternative fuels from renewable sources. Due to its abiotic stress tolerance and annual cultivation, high-biomass sorghum (Sorghum bicolor L. Moench) shows potential as a bioenergy crop. Genomic selection is a useful tool for accelerating genetic gains and could restructure plant breeding programs by enabling early selection and reducing breeding cycle duration. This work aimed at predicting breeding values via genomic selection models for 200 sorghum genotypes comprising landrace accessions and breeding lines from biomass and saccharine groups. These genotypes were divided into two sub-panels, according to breeding purpose. We evaluated the following phenotypic biomass traits: days to flowering, plant height, fresh and dry matter yield, and fiber, cellulose, hemicellulose, and lignin proportions. Genotyping by sequencing yielded more than 258,000 single-nucleotide polymorphism markers, which revealed population structure between subpanels. We then fitted and compared genomic selection models BayesA, BayesB, BayesCπ, BayesLasso, Bayes Ridge Regression and random regression best linear unbiased predictor. The resulting predictive abilities varied little between the different models, but substantially between traits. Different scenarios of prediction showed the potential of using genomic selection results between sub-panels and years, although the genotype by environment interaction negatively affected accuracies. Functional enrichment analyses performed with the marker-predicted effects suggested several interesting associations, with potential for revealing biological processes relevant to the studied quantitative traits. This work shows that genomic selection can be successfully applied in biomass sorghum breeding programs.     

DNA barcoding of metacestodes found in the Guerlinguetus ingrami (Rodentia: Sciuridae) reveals the occurrence of Hydatigera taeniaeformis sensu stricto (Cyclophyllidea: Taeniidae) in the Americas

The existence of cryptic species in the genus Hydatigera, cyclophillid cestodes, mainly of felids, was recently described based on molecular studies of parasites from Asia, Europe and Africa. However, the occurrence of H. taeniaeformis sensu stricto (s.s.), the species more widely distributed and with a presumed specificity for murid rodents as intermediate hosts, has not been formally described in Americas. In the present study, during necropsy of an Ingram's squirrel specimen, Guerlinguetus ingrami, found dead in the municipality of Belo Horizonte, Minas Gerais state, Brazil, strobilocerci were found in the liver. The metacestodes were subjected to morphological and molecular studies. Sequences of the COI barcode region were obtained and used for phylogenetic analyses. The morphology and measures of the rostellar hooks were compatible with the ones described for H. taeniaeformis s.s. This identification was confirmed by a molecular phylogenetic approach (96.2–99.7% similarity with isolates of the parasite from Europe and Asia). This is the first molecular confirmation of the existence of H. taeniaeformis s.s. on the American continent. Moreover, the involvement of sciurid rodents in the transmission of H. taeniaeformis s.s. is discussed here as a probable case of parasite spillover.     

Lagged Population Growth in a Termite Host Colony: Cause or Consequence of Inquilinism?

The presence of foreign organisms in the colonies of social insects could affect energy allocation to growth and reproduction of these hosts. Highly specialized invaders of such long-lived hosts, however, can be selected to be less harmful. After all, it pays for these symbionts to keep their host’s good health thereby prolonging cohabitation in the homeostatic environment of the termite colony. Here, we investigated such a hypothesis, focusing on populational parameters of a termite host sharing its nest with an obligatory termite inquiline. To this end, 19 natural colonies of Constrictotermes cyphergaster (Silvestri, 1901) (Termitidae: Nasutitermitinae) were sampled and the (i) number of individuals, (ii) proportion of soldier/workers in the colonies, and (iii) presence/absence of obligatory inquiline Inquilinitermes microcerus (Silvestri, 1901) (Termitidae: Termitinae) were measured. Results revealed a negative correlation between the number of individuals and the proportion of soldier/workers in the host colonies with the presence of I. microcerus colonies. In search of causal mechanisms for such a correlation, we inspected life history traits of both, inquilines and hosts, hypothesizing that such a result could indicate either (i) a dampening effect of the inquiline upon its host population or (ii) the coincidence of the moment of inquiline infiltration with the natural reduction of C. cyphergaster populational growth at the onset of its reproductive phase.     

Evaluation of Probiotic Potential of Bacteriocinogenic Lactic Acid Bacteria Strains Isolated from Meat Products

In this study, the probiotic potential of five bacteriocin-producing lactic acid bacteria (LAB) strains, isolated from meat products, was investigated. They were presumptively identified as Lactococcus lactis subsp. cremoris CTC 204 and CTC 483, L. lactis subsp. hordinae CTC 484, and Lactobacillus plantarum CTC 368 and CTC 469 according to morphological, biochemical, and physiological characteristics. Analysis of genetic variability (random amplified polymorphic (RAPD)-PCR) and whole-cell proteins (SDS-PAGE) revealed similarity between Lactobacillus strains and variability among Lactococcus strains. The evaluation of the probiotic potential showed that the five LAB strains were tolerant to pH 2.0, and only strain CTC 469 was tolerant to the lowest concentration of the bile salts evaluated (0.1%). All strains showed survival or growth ability at 4, 25, and 37 °C, and tolerance at ??20 °C. Although strain CTC 204 in TSB Broth supplemented with MgSO₄ showed the highest intensity of biofilm production, this compound was produced by all of them. The safety assessment showed that no thermonuclease, hemolytic, or gelatinase activities were detected. All strains were resistant to erythromycin and sensitive to amoxicillin and phenoxymethylpenicillin; furthermore, CTC 204 was resistant to chloramphenicol, CTC 368 and CTC 469 to chloramphenicol and vancomycin, CTC 483 to tetracycline and vancomycin, and CTC 484 to clindamycin and chloramphenicol. The evaluated strains showed biogenic amine production; the lowest levels were produced by CTC 204 and CTC 368 strains. It was concluded that CTC 204 and CTC 368 strains have the greatest potential for becoming probiotics.     

A molecular approach to drought‐induced reduction in leaf CO2 exchange in drought‐resistant Quercus ilex

Drought‐induced reduction of leaf gas exchange entails a complex regulation of the plant leaf metabolism. We used a combined molecular and physiological approach to understand leaf photosynthetic and respiratory responses of 2‐year‐old Quercus ilex seedlings to drought. Mild drought stress resulted in glucose accumulation while net photosynthetic CO₂ uptake (P_n) remained unchanged, suggesting a role of glucose in stress signaling and/or osmoregulation. Simple sugars and sugar alcohols increased throughout moderate‐to‐very severe drought stress conditions, in parallel to a progressive decline in P_n and the quantum efficiency of photosystem II; by contrast, minor changes occurred in respiration rates until drought stress was very severe. At very severe drought stress, 2‐oxoglutarate dehydrogenase complex gene expression significantly decreased, and the abundance of most amino acids dramatically increased, especially that of proline and γ‐aminobutyric acid (GABA) suggesting enhanced protection against oxidative damage and a reorganization of the tricarboxylic cycle acid cycle via the GABA shunt. Altogether, our results point to Q. ilex drought tolerance being linked to signaling and osmoregulation by hexoses during early stages of drought stress, and enhanced protection against oxidative damage by polyols and amino acids under severe drought stress.