Beta-barrel outer membrane proteins of Gram-negative bacteria are inserted into the outer membrane by the BAM (beta-barrel assembly machinery) complex. In addition, many Gram-negative bacteria harbour a related complex, called the TAM (translocation and assembly machinery). The role of this second complex is not fully understood, but it is needed for the assembly of some autotransporters and pili. An international team of investigators from the UK, Germany, Norway and Australia, including AROM’s Jack Leo, investigated the requirement of the TAM and some BAM components for the assembly of trimeric autotransporter adhesins, a group of large, adhesive surface proteins that are involved in several diseases. The study shows that of the two complexes, only the essential core components of the BAM – BamA and BamD – are required for outer membrane incorporation and surface exposure of these proteins. Thus, these components might be targeted by novel anti-infective or antimicrobial compounds to prevent binding of bacteria to host cells.
Rooke JL, Icke C, Wells TJ, et al. BamA and BamD are essential for the secretion of trimeric autotransporter adhesins. Front Microbiol. 2020; doi.org/10.3389/fmicb.2021.628879.
Enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC, respectively) are major causes of diarrhoeal disease. To cause disease, EPEC and EHEC must bind to the cells of the intestine. This causes rearrangements of the cell surface, resulting in a “pedestal” around the bacteria. The formation of this structure is necessary for intimate attachment of the bacteria to intestinal cells, which in turn is necessary for diarrhoea to develop.
Pedestal formation depends on a surface protein called intimin, which is an adhesin that mediates the intimate attachment of the pathogens to the intestinal cells. The adhesive tip of intimin is projected away from the bacterial surface by several tandemly arranged immunoglobulin (Ig)-like domains that form the “stalk” of the protein.
Jack C. Leo and colleagues from Denmark, Norway, Sweden, Germany and Japan have solved the structure of two of the Ig-like domains, called D00 and D0, which are located at the beginning of the stalk. These have been the final missing pieces which allow full structural modelling of the extracellular region of intimin. The short connector between these two domains is rigid, whereas the connectors between the other Ig-like domains are more flexible. Using computer modelling, the researchers show that this arrangement of rigid and flexible regions increases the overall reach of the adhesin, i.e. allows it to project further on average from the bacterial surface than if all the connectors were flexible. The flexibility of some parts, on the other hand, could help the adhesin bind to its receptor on the host cell surface.
Weikum J, Kulakova A, Tesei G., et al. The extracellular juncture domains in the intimin passenger adopt a constitutively extended conformation inducing restraints to its sphere of action. Sci Rep. 2020; doi.org/10.1038/s41598-020-77706-7.
Dr Jody Winter recently contributed to a successful ERASMUS+ International Credit Mobility bid that will allow Microbiology staff and students from NTU and Makerere University, Uganda to take part in exchange visits to each other's universities. The project, funded for the next 3 years, will see NTU and Makerere students taking part in summer research placements in Uganda and the UK, respectively. This will be a unique opportunity for UK-based and African students to experience different educational environments and to work on projects that will contribute to strengthening research links between microbiologists at Makerere University and NTU.
The NTU Microbiology team, led by Dr Jody Winter, will also support joint research projects on plants with antimicrobial activities between NTU, Jomo Kenyatta University of Agriculture and Technology, Mount Kenya University and Brackenhurst Kenya Ltd as part of a second funded ERASMUS+ International Credit Mobility project.
We are delighted to contribute to these projects and look forward to welcoming African microbiologists to NTU in the (hopefully) not-too-distant future.
Antimicrobial stewardship promotes responsible use of antimicrobials to prevent the development of antimicrobial resistance. Implementation of antimicrobial stewardship remains poor in many low- and middle-income countries. Using a one-health approach, for the past 2 years a team of academics from Nottingham Trent University and Makerere University, Uganda and pharmacists and healthcare professionals from Buckinghamshire Healthcare NHS Trust have been working together on a project to strengthen antimicrobial stewardship in Wakiso District, Uganda. You can read all about the excellent outcomes from this exciting project here.
Musoke D, Kitutu FE, Mugisha L, et al. A one health approach to strengthening antimicrobial stewardship in Wakiso District, Uganda. Antibiotics. 2020; doi.org/10.3390/antibiotics9110764.
This is not the end of NTU and AROM’s work on antimicrobial stewardship and resistance in Uganda. As part of a recently funded ERASMUS project, microbiology students from NTU and Makerere University will have the opportunity to work at each other’s universities on joint summer research placements. This will be a unique opportunity for UK-based and African students to experience different educational environments and to work on projects that will contribute to strengthening research links between Makerere University and NTU.
The NTU Microbiology team, led by Dr Jody Winter, will also support joint research projects on plants with antimicrobial activities between NTU, Jomo Kenyatta University of Agriculture and Technology, Mount Kenya University and Brackenhurst Kenya Ltd as part of a second recently funded ERASMUS programme.
We're delighted our work with colleagues at the University of East Anglia and the Quadram Institute has been published.
Using faecal microbiota transplants in mice, we have shown that giving the gut microbiota of old mice to young mice has measurable effects on the central nervous system. This work has important implications for understanding how aging and the microbiota influence neurological function, and may allow us to develop methods to target the microbiota to assist 'healthy aging'. Watch the video below to find out more about this exciting work!
D’Amato, A., Di Cesare Mannelli, L., Lucarini, E. et al. Faecal microbiota transplant from aged donor mice affects spatial learning and memory via modulating hippocampal synaptic plasticity- and neurotransmission-related proteins in young recipients. Microbiome. 2020;doi.org/10.1186/s40168-020-00914-w.
Trimeric autotransporter adhesins (TAAs) are a family of surface proteins from Gram-negative bacteria. As their name implies, these proteins mediate binding of the bacteria to a variety of surfaces, including host cells and matrix components, abiotic surfaces, and other bacteria. This latter ability is called autoaggregation, which is a widespread phenomenon among bacteria and confers protection against environmental threats. The autoaggregation mediated by TAAs is homotypic, i.e. the TAAs bind to themselves.
In a recent paper, Jack C. Leo and colleagues have investigated whether TAAs can also mediate heterotypic binding to other types of TAAs. This would lead to co-aggregation of bacteria producing different TAAs. To do this, Leo and colleagues genetically engineered laboratory Escherichia coli to produce a specific type of TAA as well as a fluorescent marker protein, either red or green. Using microscopy and software prepared for this study, the researchers quantified the interactions between two populations of bacteria producing the same (autoaggregation) or different TAAs (co-aggregation).
The results show that different TAAs can mediate co-aggregation, and generally the degree of co-aggregation correlated with the sequence similarity between the interacting TAAs. However, in some cases, two TAAs excluded each other, and aggregates of only one type of bacteria were formed. These findings have implications for the ecology of bacteria: co-aggregation is often a sign of co-operation between bacteria, whereas exclusion might indicate competition.
Khalil HS, Øgaard J, Leo JC. Coaggregation properties of trimeric autotransporter adhesins. MicrobiologyOpen. 2020;doi:10.1002/mbo3.1109.
In their recently published review, Rachel Whelan, Gareth McVicker and Jack C. Leo from the AROM group delve into the relationship between type 3 secretion systems (T3SSs) and type 5 secretion systems (T5SSs), providing an in-depth analysis of their roles in adhesion, invasion and their collaborative role in pathogenesis in Gram-negative bacteria. T3SSs form a syringe-like structure able to transport effector proteins into the host cell. T5SSs, also referred to as autotransporters, are known for their independent transport to the bacterial cell surface where they carry out a diverse array of functions, ranging from adhesion to immune evasion. This review discusses the interplay between the T3SSs and T5SSs that aid pathogenesis of some of the most well studied enteropathogenic organisms such as the Yersiniae, Shigella spp., enteropathogenic Escherichia coli and enterohaemorrhagic E. coli. The pathogenesis of these organisms relies heavily on the two secretion systems acting collectively to achieve virulence, resulting in host cell invasion, intra- and inter-cellular motility and evasion of the immune response, leading to changes in the host cell cytoskeleton which is central to disease.
Whelan R, McVicker G, Leo JC. Staying out or going in? The interplay between type 3 and type 5 secretion systems in adhesion and invasion of enterobacterial pathogens. Int J Mol Sci. 2020;doi:10.3390/ijms21114102.
Supervised by Dr Jody Winter, this paper describes work that was completed by Ben Murray and Robin Dawson (former MRes students at NTU who undertook research projects in the AROM group) and Lolwah Alsharaf, who is currently writing up her PhD thesis. They found that outer-membrane vesicles produced by Helicobacter pylori can help to protect the bacterium against hydrogen peroxide and some antimicrobial agents.
Murray B, Dawson R, Alsharaf L, Winter J. Protective effects of Helicobacter pylori membrane vesicles against stress and antimicrobial agents. Microbiology. 2020;doi.org/10.1099/mic.0.000934.
Yersinia ruckeri is a fish pathogen, causing an infection called enteric redmouth disease that affects mostly salmonid fish. The disease causes significant losses in the aquaculture industry. Like most bacteria, Y. ruckeri survives in the environment by forming biofilms. These are multicellular bacterial communities embedded in a slimy extracellular matrix composed of a variety of different molecules.
In their newly published study, Jack C. Leo and colleagues investigated the role of two surface proteins in biofilm formation in Y. ruckeri – Y. ruckeri invasin (YrInv) and Y. ruckeri invasin-like molecule (YrIlm). They had identified these proteins previously and, based on their similarity to adhesins from other bacteria, assumed both mediated attachment of Y. ruckeri to surfaces.
Knocking out the genes coding for these proteins individually significantly reduced the ability of Y. ruckeri to form a biofilm on several different types of surface, including many used in aquaculture (PVC, steel and polystyrene). When both genes were knocked out, Y. ruckeri barely formed any biofilm.
Larvae of the greater waxmoth (Galleria mellonella) were used to test whether YrInv and YrIlm also played a role in causing disease. Y. ruckeri strains unable to produce one or both proteins had to be used at much higher infectious doses than the wild-type strain to kill the larvae.
Overall, this study demonstrates that YrInv and YrIlm are adhesins of Y. ruckeri that promote biofilm formation and virulence. As such, they are potential targets for vaccine development or measures to control biofilm formation by Y. ruckeri in an aquaculture setting.
Wrobel A, Saragliadis A, Pérez-Ortega J, et al. The inverse autotransporters of Yersinia ruckeri, YrInv and YrIlm, contribute to biofilm formation and virulence. Environ Microbiol. 2020;doi:10.1111/1462-2920.15051.
On 15 February 2020 staff and students keen on microbiology and outreach braved the wind and rain to entertain and educate visitors to the Nottingham Festival of Science and Curiosity from 10 am to 4 pm in the Victoria Centre market area.
This year we were accompanied by "Geralt the Germophobe" our now 3-D body target for our activity on helpful and harmful bacteria. Visitors selected volunteer fluffy bacteria to throw at Geralt and then discovered what nice or nasty bacterium made its home in the location they had hit. After a brief explanation as to what the bacterium could do either for or against humankind each visitor received a "non top trump" card with the bacterium’s statistics and unique artwork, as well as a stylish networking sticker "Hallo my name is ...." emblazoned with the name of their newly adopted microbial friend.
There was then the opportunity to learn the importance of cleaning your teeth and not eating sweets before bed, as visitors could interact with our highly accurate biofilm model – carefully crafted from packing material and cheap hair gel. Having discovered that bacteria are much harder to remove from teeth when in a biofilm produced by conversion of sucrose to a sticky polymer, visitors were informed in breathless tones that during the night bacteria wee in your mouth while you sleep. Not at all traumatised by this they left, presumably to go buy some mouthwash and toothpaste. :-)
These activities were delivered by members of staff from the NTU microbiology team as well as NTU undergraduate students Frazer, Chloe, Sara and Ghazelle, who worked really hard and were brilliant through a long day, assisted by mini-microbiologists Holly from South Wolds Academy and Bethany from Crossdale Drive primary school.