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The 3rd International Erwinia Workshop and the 13th International Congress on Plant Pathogenic Bacteria 7th – 13th June 2014
Shanghai, China was the scene for the 3rd International Erwinia workshop (on soft rot Enterobacteriaceae and related organisms) and the 13th International Conference on Plant Pathogenic Bacteria in June 2014. About 80 people attended the workshop and 150 overseas delegates made up the 300 who attended the main meeting. The smaller workshop is now an established event held in conjunction with the main meeting, thanks to the efforts of Ian Toth and Jean Martin van der Wolf and colleagues in organising it. This was certainly the more intimate meeting allowing good discussions and observing the range of activities on going with the enteric bacteria. I particularly enjoyed the talk of Stephanus Venter who described the challenges faced in defining the genus Pantoea. Stephanus described the use of whole genomes for the analysis and the need to define the core genome for use in producing a robust species tree.
The main meeting ran from Monday to Friday with a very busy schedule and many enjoyable talks, too many to cover here. There were several high profile speakers who attended and gave excellent talks; here I describe some new developments that I hadn’t heard before. Boris Vinatzer gave a nice overview on mechanisms involved in coevolutionary arms races between patho gen and plant host, providing evidence for allelic diversity in both PAMPs and PAM P receptors. He also described the importance of chemotaxis for pathogen invasion into the plant, in doing so demonstrating the trade-off for infection and triggering of PTI. However, the pathogen has also evolved another mechanism, AprA, a protease to breakdown flagellin to help counter PTI triggering. I really enjoyed Jan Leach’s talk describing the toxin-antitoxin effects conferred by AvrRxo1:Arc1 in Escherichia coli, an intriguing new functionality. David Guttman described the elaborate genetic screen that led to the identification of the HopZ1a interactor, Zed1, a protein kinase in Arabidopsis. Max Dow provided an elegant overview of his work on the complexity of the Rpf/DSF system in Xanthomonas and, using a classic mutagenesis approach, the identification of RpfS, a second DSF sensor that is important for virulence. Cindy Morris provided a thought provoking talk on the ecological genomics and lifestyle of Pseudomonas syringae, leading the way forward in challenging the paradigm that P. syringae only lives in “host” plants i. e. it can live in a wider array of plants. Jim Alfano described progress in research on HopE1 and HopU1; of particular interest was that HopE1 requires a plant co-factor to function properly in targeting the plant microtubule network and inhibiting protein secretion (e.g. antimicrobials that would be delivered to the apoplast where the pathogen resides).
There were a range of high quality talks by early career scientists. Sandra Visnovsky gave an excellent description of work in Andrew Pitman’s group to use genomics of bacteria associated with kiwi fruit (including pathogens and non-pathogens). Through this they were able to identify pathogen-specific loci that were used as the basis for diagnostic identification of the kiwi pathogen P. syringae pv. actinidiae. The University of Pretoria/FABI provided several talks of interest; Lucy Moeleki describing Pectobacterium carotovorum subsp brasiliense colonisation of susceptible and tolerant potato cultivars; she observed clear behavioural differences in each, with bacterial motility being prevalent in the tolerant cultivar and biofilm formation occurring in the susceptible cultivar. Gaby Carstensen described a nice community analysis of bacterial exudate from Eucalyptus trees exhibiting wilt symptoms and in doing so discovered the presence of Ralstonia solanacearum; interestingly she found Enterobacter was most prevalent in healthy trees along with several other bacterial species. This indicates a significant change in the bacterial community between healthy and diseased trees.
In both meetings, I was able to give a talk, firstly on how human pathogenic Escherichia coli can inhabit and grow on plants. This was the result of PhD work by Louise Birse (based at James Hutton Institute with Nicola Holden) and Glyn Barrett, whereby each used a different type of gene expression system to identify genes induced during plant colonisation. In the main meeting I was able to describe the work of PhD student Sarah James who has been characterising bacteriophage that infect and kill Pseudomonas syringae pv. aesculi, the cause of bleeding canker of Horse Chestnut trees. Her work shows the potential of being able to treat bacterial infections in trees with a phage cocktail.
Of course, Chinese hospitality is very well known and the organisers treated delegates to a trip to Xikou to see the home town, and later secret HQ, of Chiang Kai-shek. We were able to appreciate some nice rural scenery along the way and to visit a giant Laughing Buddha statue (pictured above). The meals provided were excellent, usually swilled down with some potent “Chinese water” and the last trip included a cruise on the Huangpu river to see the Shanghai skyline at night.
My thanks to Gongyou Chen and his coorganisers who delivered a well organised and interesting pair of meetings; thanks also to BSPP for the funding, which enabled me to attend these meetings.
Robert W. Jackson University of Reading
The Erwinia workshop presents a special opportunity for researchers working on soft rot Enterobacteriaceae and related organisms to come together and share their work to discuss progress, achievements and challenges. It is a very friendly platform and often much more interactive and focused on solving specific problems. In this year’s workshop, the big concerns were on the three emerging soft rot pathogens. Pectobacterium brasiliense, which was first reported in Brazil but appears to be much more widespread than initially thought. Hence one of the question is should we still call it P. brasiliense? Pectobacterium wasabiae is another emerging species of concern and of course, in Europe the biggest concern remains Dickeya solanii In terms of interesting research trends within the soft rot Enterobacteriaceae community comparative genomics is gaining momentum and revealing interesting new pathogenicity factors. In this respect, Eva Lojkowska, Frederique Van Gijsegem and Andrew Pitman successfully used this approach to identify new virulence factors and adaptive strategies of Dickeya and Pectobacterium spp. Currently, there are more advances and understanding of xylem dwelling pathogens such as Xanthomonas and Xylella, but very little work has been done towards understand how soft rot pathogens colonise the xylem. Hence, of particular interest to me is the presentation of Andrew Pitman on the mechanisms that are utilised by those soft rot pathogens that cause blackleg. Another interesting talk at the workshop was by Linda Garlant, who presented a paper on a bacteriocin-like molecule produced by Dickeya solani. This is interesting given the growing importance of toxins in bacterial competition.
The conference kicked off immediately after workshop with a special talk given by Jacob Janse. This was a great overview that gave perspectives, challenges as well as the future direction of phytobacteriology. The talk spanned approximately 38 years of the ‘history’ of phytobacteriology. Hence it was packed with information from detection of emerging pathogens, and general prevention and control of different phytopathogenic bacteria including Dickeya spp. , Xylella fastidiosa and Candidatus Liberibacters. Of course, a phytobacteriology meeting would not be complete without the dominance of T3SS effectors, and the interplay between the host and the pathogen in the form of PTI and ETI. The massive progress that has been achieved in Pseudomonas syringae and Xanthomonas spp. host interactions was clearly visible with many groups presenting on these pathogens. Quorum sensing also remains an important player in bacteria virulence. Hence, the talk by Steven Lindow showing their achievements towards control of Xylella fastidiosa through understanding of this density dependant behaviour is a worthy example of application. Another three interesting emerging areas of research are the roles of toxinantitoxins, small signalling molecule cdi- GMP and small regulatory RNAs in phytopathogenic bacteria. In this respect, three talks caught my attention, one by Jan Leach showing that the Xanthomonas effector AvrRxo1 and its chaperone Arc1 act as a toxin antitoxin system, another one by Shigi An on c-di -GMP in Xanthomonas campestris, and finally by Bin Li and co-authors used RNA seq to discover, among other things, sRNA in Burkholderia seminalis.
This was a great scientific experience for me. I was also able to present a talk at the Erwinia workshop and another at the ICPPB congress. I received numerous comments and suggestions for both presentations. I would like to thank BSPP for their generous award that made my attendance possible.
Lucy Moleleki University of Pretoria, South Africa
