Publications

3807

Genome analysis is one of the main criteria for description of new taxa. Availability of genome sequences for all the actinobacteria with a valid nomenclature will, however, require another decade’s works of sequencing. This paper describes the rearrangement of the higher taxonomic ranks of the members of the phylum ‘ Actinobacteria ’, using the phylogeny of 16S rRNA gene sequences and supported by the phylogeny of the available genome sequences. Based on the refined phylogeny of the 16S rRNA gene sequences, we could arrange all the members of the 425 genera of the phylum ‘ Actinobacteria ’ with validly published names currently in use into six classes, 46 orders and 79 families, including 16 new orders and 10 new families. The order Micrococcales Prévot 1940 (Approved Lists 1980) emend. Nouioui et al. 2018 is now split into 11 monophyletic orders: the emended order Micrococcales and ten proposed new orders Aquipuribacterales , Beutenbergiales , Bogoriellales , Brevibacteriales , Cellulomonadales , Demequinales , Dermabacterales , Dermatophilales , Microbacteriales and Ruaniales . Further, the class ‘ Actinobacteria ’ Stackebrandt et al. 1997 emend. Nouioui et al. 2018 was described without any nomenclature type, and therefore the name ‘ Actinobacteria ’ is deemed illegitimate. In accordance to Rule 8 of the International Code of Nomenclature of Prokaryotes, Parker et al. 2019, we proposed the name Actinomycetia which is formed by using the stem of the name Actinomycetales Buchanan 1917 (Approved Lists 1980) emend. Zhi et al. 2009, to replace the name ‘ Actinobacteria ’. The nomenclature type of the proposed new class Actinomycetia is the order Actinomycetales Buchanan 1917 (Approved Lists 1980) emend. Zhi et al. 2009.

AbstractPhytoplasmas are specialized small bacteria restricted to the phloem tissue and spread by hemipterans feeding on plant sieve tube elements. As for many other plant pathogens, it is known that phytoplasmas alter the chemistry of their hosts. Most research on phytoplasma-plant interactions focused on the induction of plant volatiles and phytohormones. Little is known about the influence of phytoplasma infections on the nutritional composition of phloem and consequences on vector behavior and development. The plum psyllid Cacopsylla pruni transmits ‘Candidatus Phytoplasma prunorum’, the causing agent of European Stone Fruit Yellows (ESFY). While several Prunus species are susceptible for psyllid feeding, they show different responses to the pathogen. We studied the possible modulation of plant-insect interactions by bacteria-induced changes in phloem sap chemistry. Therefore, we sampled phloem sap from phytoplasma-infected and non-infected Prunus persica and Prunus insititia plants, which differ in their susceptibility to ESFY and psyllid feeding. Furthermore, the feeding behavior and development of C. pruni nymphs was compared on infected and non-infected P. persica and P. insititia plants. Phytoplasma infection did not affect phloem consumption by C. pruni nymphs nor their development time. In contrast, the study revealed significant differences between P. insititia and P. persica in terms of both phloem chemistry and feeding behavior of C. pruni nymphs. Phloem feeding phases were four times longer on P. insititia than on P. persica, resulting in a decreased development time and higher mortality of vector insects on P. persica plants. These findings explain the low infestation rates of peach cultivars with plum psyllids commonly found in field surveys.

Chain elongation by medium-chain fatty acid (MCFA)-producing microbiomes offers an opportunity to produce valuable chemicals from organic streams that would otherwise be considered waste. However, the physiology and energetics of chain elongation are only beginning to be studied, and many of these organisms remain uncultured. We analyzed MCFA production by two uncultured organisms that were identified as the main MCFA producers in a microbial community enriched from an anaerobic digester; this characterization, which is based on meta-multi-omic analysis, complements the knowledge that has been acquired from pure-culture studies. The analysis revealed previously unreported features of the metabolism of MCFA-producing organisms.