Newsletter September 2017

Next BSM Symposium

Don’t forget our symposium Current Highlights in Microbiology held on October 20th, in Brussels. Programme here.

The deadline for abstract submission, September 30th, 2017, is approaching! Abstracts are for posters. Posters will be exhibited during the lunch and coffee break. Attention:  poster panels are maximum 1 meter in width. Four poster prizes (each of 100 €), for the best poster in each section, will be given at the end of the meeting.

The best abstracts will be selected by the BSM board (before the meeting) for an oral presentation of ca. 10 min. Two abstracts will therefore be selected in each of the 4 BSM sections. Abstracts selected for an oral presentation will receive notice by email, before October 11th. If you do not receive any message from BSM after October 11th, this means that your abstract has not been selected for an oral presentation. A prize will also be given for the best oral presentation.

PhD defense on Rhodospirillupm rubrum at the Mons University

Quentin De Meur will present his PhD thesis entitled “Rhodospirillum rubrum S1H: unravelling the volatile fatty acids assimilation in the MELISSA loop.” UMons, October 6th, 15:00, Vésale 25.

Purple non-sulfur bacteria (PNSB) represent a promising resource for existing and future biotechnologies. These organisms are characterized by a large metabolic versatility and might be used in various biotechnology sectors such as biofuel synthesis,  biodegradable plastic production, wastewater treatment, or biofertilization. Rhodospirillum rubrum is an α-Proteobacterium. It was selected by the European Space Agency (ESA) to colonize the second compartment of the MELiSSA loop, the life support system envisaged to autonomously sustain a crew for a long-term space mission. Indeed, under anaerobic condition, R. rubrum is able to grow photoheterotrophycally with light as energy source and simple organic compounds like acetate as a carbon source. In the MELiSSA loop, simple organic compounds are mainly the volatile fatty acids (VFA) produced in the first compartment. More than half of these VFA is acetate followed, in order of decreasing abundance, by butyrate, isobutyrate, valerate and propionate. The metabolism used by the bacterium during photoheterotrophic growth on acetate and butyrate was the subjects of this thesis.

In order to assimilate acetate, the citramalate cycle was proposed in R. rubrum but never clearly demonstrated. The combination of proteomics and functional genomic approaches highlighted here that the Ethylmalonyl-CoA pathway (the EMC) was the main pathway for acetate photoassimilation in R. rubrum. Our investigations also highlighted an increased light stress sensibility during the early growth phase when acetate is the carbon source. We linked this phenomenon with a redox imbalance since the addition of carbonate (the fixation of which is known to be an electron sink) in the culture medium allowed to reduce it significantly. An acetate-acclimatization phenomenon reducing this sensibility has also been observed and has been linked to the amplification of a 60 kb fragment in the genome of the bacteria. This fragment contained the key enzymes of the EMC pathway which is involved in the carbonate fixation and in the reduced cofactors regeneration. This observation highlights for the first time the involvement of genomic plasticity (in this case duplication of an operon) which was already known to be prevalent in  antibiotic or metal-resistance phenomena. Such an adaptation mechanism help the bacterium to regulate its redox homeostasis.

PhD defense on the interaction of bacteria with volcanic rocks on Earth and in space at the Ghent University.

Ir. Bo Byloos will present his PhD thesis entitled “The interaction of bacteria with volcanic rocks on Earth and in space” at the Ghent University, on September 27th, 2017, at 16:00 at the UGent. Invitation to the PhD Public Defense.

Microorganisms can interact with minerals for sustaining their survival and growth. These microbe-mineral interactions are involved in bioweathering processes, and have already proved their relevance in agricultural and industrial applications such as enhancing soil fertility, biorestoration, bioremediation and biomining. More recently, microbe-mineral interactions have also become of interest for space exploration missions as they could generate nutrients from ‘in-situ material” (ISRU) such as the regolith and rocks. This will reduce the costs and dependency for supplies from Earth and could support a long-term human presence in space.

Basalts in Iceland

In our study, the interaction of the bacterium Cupriavidus metallidurans CH34 with basalt, a volcanic moon-analog rock, was investigated. The bacterial presence on basalt and its impact on weathering, as well as the effect of basalt composition on nutrient leaching was studied. Differences in lava flow composition, as well as the age of the deposits contributed to shape the microbial communities in terrestrial volcanic rocks, which affects weathering rates and nutrient availability. Different basalt compositions were also shown to impact nutrient leaching and subsequently impact bacterial growth. In addition, survival and the potential impact of space environmental conditions such as microgravity on these interactions were determined, probing the potential of ISRU. Our results indicated that basalt had a positive effect on survival through the release of elements such as sodium, potassium, and phosphate, counteracting some of the detrimental effects of starvation. Space flight conditions in addition also a positive effect on survival while cells form less biofilm. This study contributes to a better understanding of microbe-mineral interactions, opening the door to future applications, in space, and on Earth.

Cupriavidus metallidurans CH34 on basalts