Developmental stages and gut microenvironments influence gut microbiota dynamics in the invasive beetle Popillia japonica Newman (Coleoptera: Scarabaeidae)

Popillia japonica Newman (Coleoptera: Scarabaeidae) is a highly polyphagous invasive beetle originating from Japan. This insect is highly resilient and able to rapidly adapt to new vegetation. Insect?associated microorganisms can play important roles in insect physiology, helping their hosts to adapt to changing conditions and potentially contributing to an insect's invasive potential. Such symbiotic bacteria can be part of a core microbiota that is stably transmitted throughout the host's life cycle or selectively recruited from the environment at each developmental stage. The aim of this study was to investigate the origin, stability and turnover of the bacterial communities associated with an invasive population of P. japonica from Italy. Our results demonstrate that soil microbes represent an important source of gut bacteria for P. japonica larvae, but as the insect develops, its gut microbiota richness and diversity decreased substantially, paralleled by changes in community composition. Notably, only 16.75% of the soil bacteria present in larvae are maintained until the adult stage. We further identified the micro?environments of different gut sections as an important factor shaping microbiota composition in this species, likely due to differences in pH, oxygen availability and redox potential. In addition, P. japonica also harboured a stable bacterial community across all developmental stages, consisting of taxa well known for the degradation of plant material, namely the families Ruminococcacae, Christensenellaceae and Lachnospiraceae. Interestingly, the family Christensenallaceae had so far been observed exclusively in humans. However, the Christensenellaceae operational taxonomic units found in P. japonica belong to different taxonomic clades within this family

Phylogenetic analysis of the bacterial genus Thermobacteroides indicates an ancient origin of Thermobacteroides proteolyticus

The phylogenetic position of two validly described species of Thermobacteroides, T. acetoethylicus and T. proteolyticus was determined by sequence analysis of their 16S rDNA. Comparison of the data with those from more than 600 bacterial species indicated that the two species belong to phylogenetically well separated phyla. While T. acetoethylicus fell within the radiation of the Clostridium/Bacillus sub‐phylum, T. proteolyticus is a deep root to the Thermotogales. Hence, the artificial clustering of thermophilic species with Bacteroides‐type characters into the same genus is not justified from a genetic /phylogenetic point of view and highlights the importance of phylogenetic studies prior to the description of new taxa

Phylogenetic evidence for the classification of Acidothermus cellulolyticus into the subphylum of actinomycetes

The primary structure of the 16S rDNA of Acidothermus cellulolyticus, a cellulolytic, asporogenous rod isolated from a hot spring, was determined by automated sequence analysis. This Gram-variable organism is not related to members of other aerobic thermophilic genera found in similar environments, such as Thermus and Thermomicrobium, but clusters within the phylogenetically defined radiation of the actinomycetes where it represents an individual subline of descent

16S-rDNA analysis of Spirochaeta thermophila: Its phylogenetic position and implications for the systematics of the order Spirochaetales

The 16S rRNA gene of Spirochaeta thermophila DSM 6578 was amplifed by the polymerase chain reaction and analysis of a 1333 nucleotide long stretch performed. The sequence was aligned to the homologous region of 13 representatives from six spirochete genera, and the phylogenetic position of S. thermophila determined. This species constitutes a deep-branching member of a cluster that is defined by representatives of Spirochaeta and Treponema and by Borellia burgdorferi. The genera Serpulina, Leptonema and Leptospira are more ancient representatives of the spirochete line of descent. The branching pattern confirms earlier results of phylogenetic studies which showed the genus Spirochaeta to be heterogeneous, with S. zuelzerae and S. stenostrepta displaying a higher degree of relatedness to treponemas than to the main (authentic) Spirochaeta group

Spirochaeta thermophila sp. nov., an obligately anaerobic, polysaccharolytic, extremely thermophilic bacterium

Growth at temperatures of >60°C and utilization of polysaccharides have not been reported previously in members of the genus Spirochaeta. Two obligately anaerobic, extremely thermophilic (optimum temperature, 65°C) spirochetes were isolated from geographically distant thermal sites. These two isolates have chemoorganotrophic fermentative metabolism and grow on a variety of mono-, di-, and polysaccharides, including cellulose. The differences in pH and NaCl concentration optima between these organisms reflect the prevailing conditions at the sites from which they were isolated. DNA-DNA hybridization showed that the two strains exhibit a level of homology of 87%. On the basis of their morphological characteristics, their high level of homology with each other, and their extremely thermophilic and polysaccharolytic nature, we propose that these organisms should be included in the genus Spirochaeta as a new species, Spirochaeta thermophila; the type strain of this species is strain Z-1203 (= DSM 6578)