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After a long 16 h trip, our plane landing brought impressive views of the large palm plantations, used for the palm oil trade that is so (in)famous in Malaysia. This was our first ever trip to the Malaysian capital city, Kuala Lumpur, to join around 180 delegates for talks and discussion on a range of Pseudomonas species, including biomedical, environmental and plant interacting Pseudomonads. A very warm welcome was provided by the conference organiser and host Kalai Mathee – she promised us a science, cultural and food extravaganza and she wasn’t wrong!
As plant-microbe specialists, this meeting is always useful because of the range of topics brought to the fore by non-plant experts, and the field tends to be dominated by P. aeruginosa experts. However, the meeting represents an opportunity to meet with a comparatively small group of plant associated Pseudomonas experts from around the world and we highlight some of those talks below Bryan Swingle (US Department of Agriculture, Ithaca, USA) talked about Stealthy infections – Pseudomonas syringae AlgU downregulates flagellin expression helping minimize plant immune activation. Bryan is interested in understanding the changes in gene regulation that allow bacteria to get into plant tissue and survive. He talk focused on the stress response sigma facture AlgU and he used RNAseq to show that it regulates 965 P. syringae genes in the plant environment. One specific example was that AlgU downregulates flagellin gene expression helping the pathogen to evade plant immunity.
Vittorio Venturi (International Centre for Genetic Engineering and Biotechnology, Italy) gave a talk entitled Interspecies signalling in plant associated bacteria. Vittorio’s work moved away from studying pure cultures into more community based experiments including plants and investigating interspecies signalling in these complex communities. He uses P. savastanoi (olive knot disease) with Erwinia toletana (a non-pathogenic ‘resident’) in which both make the same homoserine lactone signal. He showed that the signal from the Erwinia can complement a mutation in the pathogen and restore virulence – thus, a nice example of intergenus cooperation. He then described microbiome studies using diseased and healthy plants growing in same field and examining the pathobiome vs microbiome to see how they differed. This focussed on three diseases and he observed distinct shifts in the microbiomes. Of note when examining the Dickeya zeae pathobiome, there was a high abundance of Dickeya, but also other bacterial genera were increasing in numbers (pathogen co-operators?) while others were lost (could these be beneficial microbes?).
Teresa de Kievit (University of Manitoba, Canada) gave a talk on Prey predator interactions: Pseudomonas brassicacearum DF41 biofilm formation on Caenorhabditis elegans. Teresa was interested in P. brassicacearum as a potential biocontrol agent. When examining the bacterial biofilm formation on C. elegans, it was noted that GacS was important as well as a number of other gene systems. Several of these were activated in response to predator activity of the nematode (and also observed for protozoa). Teresa noted that production of these compounds could lead to a change in the microbial community structure.
Cayo Ramos (University of Malaga, Spain) talked about Host specificity in Pseudomonas savastanoi pathovars of woody hosts: comparative genomics and gene regulation. P. savastanoi is defined into four pathovars that cause knots or cankers on woody plant species. This work focussed on investigating the host specificity determinants. They now have 20 genomes available covering all four pathovars and they data mined the genome. This led to the discovery of a core genome of about 3000 genes. Plant tests showed that there was some overlapping infectivity, for example, oleander strains can also infect olive. This led to the search for genes involved in host specificity. The Ash pathogen lacks some cytokinin- and cellulose-synthesis genes. There also appeared to be variation in the type III effector repertoire, almost certainly accounting for differences in host specificity.
David Baltrus (University of Arizona, Tucson, USA) talked about The evolution of strain specificity in Pseudomonas tailocins. ‘The enemy of my enemy is my friend’ was used as a concept to identify prophylactic means to prevent infection. David was trying to identify a durable strain-specific prophylactic. This was based on bacteria being very effective at killing each other, for example, using bacteriocins – David focussed in on a sub-set called tailocins that are phage derived bacteriocins. Early results showed that ‘painting’ tailocin on plants can prevent disease. New work is examining if it is possible to change tailocin targeting by genetic engineering.
Russell Poulter (University of Otago, Dunedin, New Zealand) talked about The trajectory of evolution in Pseudomonas syringae pv. actinidiae in New Zealand. He described the timeline of the recent Psa outbreaks which is a devastating disease of kiwi plants. He highlighted that it is a particularly interesting epidemiology of a new disease in his country. Work allowed the mapping of new strain genomes to the reference strain to look for evolution of pathogen. He described there being evidence that China is the source of the pandemic. He also highlighted that growers care about the evolution of copper resistance, which probably occurs via though horizontal gene transfer. Indeed, resistance to copper did emerge rapidly with the earliest observation being in 2014, just a couple of years after the pathogen entered the country. Now, the dominant Psa population in NZ is copper resistant and this occurs via acquisition of either a mega-plasmid or an ICE element integrating into tRNA-Lys site on the chromosome. Other plasmids were also observed, but their function remains cryptic. We were grateful for the opportunity to provide updates on our research.
Dawn’s keynote talk was entitled A persistent reservoir of a genomic island in Pseudomonas syringae pv. phaseolicola. She described work on a genomic island that carries an effector gene and the island can be lost during plant-immunity selection pressure. However the island persists in the bacterial population and has not been observed to go extinct in the population. This work had shown that once the island excises from the genome it circularises and gene expression of the 100 genes carried by the island is changed. It appears that this is a potential mechanism to retain the island in a small proportion of the bacterial population while avoiding the host resistance response. Rob gave an offered talk entitled An aphid-killing Pseudomonas bacterium utilizes multiple toxins to kill the insect. This described the discovery and characterisation of this bacterium, using RNAseq to identify candidate toxins, which could then be validated via gene deletions.
The traditional conference tour involved a very long but hugely enjoyable day of visiting temples, avoiding thieving monkeys, and seeing new architecture in Putrajaya and downtown KL. This was completed with a banquet of delicious Malaysian foods and dancing, before heading back to the hotel for one last conference cocktail – a ‘Kalai Lumpur’!
Our thanks go to BSPP for the support to attend this conference and to all who were involved in organising it.
Dawn Arnold (UWE Bristol) and Robert Jackson (University of Reading) The conference provided the latest discoveries and in-depth information on Pseudomonas in plant pathology and related fields. The conference started with an opening reception, which gave me the opportunity to get to know other attendees and speakers. During the week, I attended all scientific sessions including environmental sensing, antimicrobial resistance, metabolism and physiology.
I presented a poster on ‘Characterization of bacteriophage for biocontrol of Pseudomonas syringae, causative agent of canker in Prunus spp. ‘ and had the opportunity to give a 2-minute presentation, summarising my research in front of a huge crowd. It was a great experience to present my work and to be able to discuss my research afterward with great deal of interests.
On day four of the conference, we had a tour around Kuala Lumpur and learnt so much about its amazing cultural diversity. We had lunch at a banana leaf restaurant where traditional meals were served on a banana leaf and we could only eat with hands, which was a unique experience. The final celebration night was a great way to wrap up the meeting and make one final connection with colleagues and friends with plenty of food, drinks, music and dance!
The trip to Malaysia could not have ended without visiting the beautiful Tioman island, off the east coast of Malaysia, which is one of the world’s most beautiful islands. I enjoyed the crystal-clear water with snorkelling and scuba diving. I would like to thank the BSPP for providing me the travel award and giving me this unforgettable experience. Thank you!
Dr Mojgan Rabiey, PDRA University of Reading
