Lactobacilli are a diverse group of species that occupy diverse nutrient-rich niches associated with humans, animals, plants and food. They are used widely in biotechnology and food preservation, and are being explored as therapeutics. Exploiting lactobacilli has been complicated by metabolic diversity, unclear species identity and uncertain relationships between them and other commercially important lactic acid bacteria. The capacity for biotransformations catalysed by lactobacilli is an untapped biotechnology resource. Here we report the genome sequences of 213 Lactobacillus strains and associated genera, and their encoded genetic catalogue for modifying carbohydrates and proteins. In addition, we describe broad and diverse presence of novel CRISPR-Cas immune systems in lactobacilli that may be exploited for genome editing. We rationalize the phylogenomic distribution of host interaction factors and bacteriocins that affect their natural and industrial environments, and mechanisms to withstand stress during technological processes. We present a robust phylogenomic framework of existing species and for classifying new species.

a b s t r a c tLaboratory tests were conducted to investigate the effect of wetting-drying (W-D) cycles on the initiation and evolution of cracks in clay layer. Four identical slurry specimens were prepared and subjected to five subsequent W-D cycles. The water evaporation, surface cracks evolution and structure evolution during the W-D cycles were monitored. The effect of W-D cycles on the geometric characteristics of crack patterns was analyzed by image processing. The results show that the desiccation and cracking behaviour was significantly affected by the applied W-D cycles: the measured cracking water content θ c , surface crack ratio R sc and final thickness h f of the specimen increased significantly in the first three W-D cycles and then tended to reach equilibrium; the formed crack patterns after the second W-D cycle were more irregular than that after the first W-D cycle; the increase of surface cracks was accompanied by the decrease of pore volume shrinkage during drying. In addition, it was found that the applied W-D cycles resulted in significant rearrangement of specimen structure: the initially homogeneous and non-aggregated structure was converted to a clear aggregated-structure with obvious inter-aggregate pores after the second W-D cycle; the specimen volume generally increased with increasing cycles due to the aggregation and increased porosity. The image analysis results show that the geometric characteristics of crack pattern were significantly influenced by the W-D cycles, but this influence was reduced after the third cycle. This is consistent with the observations over the experiment, and indicates that the image processing can be used for quantitatively analyzing the W-D cycle dependence of clay desiccation cracking behaviour.

Problems related to unsaturated soils are frequently encountered in geotechnical or environmental engineering works. In most cases, for simplicity, one can study the problems by considering the suction effects on volume change or shear strength under isothermal conditions. Often, under these conditions, a temperature-independent water retention curve is considered in the analysis -obviously a simplification. When the temperature changes are too significant to be ignored, it is necessary to account for the thermal effects. This note presents a method for controlling suction with the vapour equilibrium technique at different temperatures. First, calibration of various saturated saline solutions was carried out at temperatures ranging from 20°C to 60°C. A mirror psychrometer was used to measure relative humidity generated by saturated saline solutions at different temperatures. The results obtained were in good agreement with the data from the literature. This information was then used to determine the water retention properties of MX80 clay, which showed that the retention curve shifts downward with increasing temperature. Résumé :On rencontre fréquemment des problèmes reliés aux sols non saturés dans des travaux de génie géotechnique ou environnemental. Dans la plupart des cas, dans un but de simplicité, les problèmes sont étudiés en considérant les effets de succion sur le changement de volume ou sur la résistance au cisaillement dans des conditions isothermes. Dans ces conditions, on considère très souvent dans l'analyse une courbe de rétention d'eau indépendante de la tempé-rature, ce qui est de toute évidence une simplification. Lorsque les changements de température sont trop importants pour être négligés, il est nécessaire de prendre en compte les effets thermiques. Dans cet article, on présente une mé-thode pour contrôler la succion au moyen d'une technique d'équilibre de vapeur à différentes températures. Première-ment, on a déterminé un étalonnage de diverses solutions salines saturées, à des température de 20°C à 60°C. Un miroir psychromètre a été utilisé pour mesurer l'humidité relative générée par des solutions salines saturées à différen-tes températures. Les résultats obtenus concordent bien avec les données de la littérature. Cette information a alors été utilisée pour déterminer les propriétés de rétention d'eau de l'argile MX80, ce qui a montré que la courbe de rétention se déplace vers le bas lorsque la température augmente.Mots clés : technique d'équilibre de vapeur, hygromètre, courbe de rétention d'eau, effets de température, bentonite compactée.[Traduit par la Rédaction] Tang and Cui 296

Bifidobacteria are well known for their human health-promoting effects and are therefore widely applied in the food industry. Members of the Bifidobacterium genus were first identified from the human gastrointestinal tract and were then found to be widely distributed across various ecological niches. Although the genetic diversity of Bifidobacterium has been determined based on several marker genes or a few genomes, the global diversity and evolution scenario for the entire genus remain unresolved. The present study comparatively analyzed the genomes of 45 type strains. We built a robust genealogy for Bifidobacterium based on 402 core genes and defined its root according to the phylogeny of the tree of bacteria. Our results support that all human isolates are of younger lineages, and although species isolated from bees dominate the more ancient lineages, the bee was not necessarily the original host for bifidobacteria. Moreover, the species isolated from different hosts are enriched with specific gene sets, suggesting host-specific adaptation. Notably, bee-specific genes are strongly associated with respiratory metabolism and are potential in helping those bacteria adapt to the oxygen-rich gut environment in bees. This study provides a snapshot of the genetic diversity and evolution of Bifidobacterium, paving the way for future studies on the taxonomy and functional genomics of the genus.

When drying a clayey soil, shrinkage and then cracking on soil surface occur due to water loss by evaporation, this phenomenon seems to be temperature dependent. In the present work, experimental tests were conducted on saturated slurry to investigate the desiccation cracking behavior at three temperatures (22, 60 and 105 °C). The initiation and propagation of desiccation cracks during drying was monitored using a digital camera. By applying computer image processing technique, the surface crack ratio (R SC ) which is the ratio of the surface area of cracks to the total surface area of specimen, was defined to quantify crack networks at different water contents. The experimental results show that the initial critical water content (w IC ), which corresponds to the initiation of desiccation crack, increases with temperature rise. After the initiation of a crack, the ratio R SC increases with decreasing water content and then keeps almost constant when the water content becomes lower than the critical water content (w FC ). By comparing the cracking curve with shrinkage curve, it has been found that the cracking curve, to some extent, reflects the shrinkage properties of soil since the w FC is related to the shrinkage limit and slightly influenced by temperature.