August's Paper of the Month

Bacteria must be able to find food in order to survive. They have evolved various chemotactic strategies to efficiently locate and track nutrient gradients, several of which have been defined. The strategies usually consist of a series of run phases in which the bacteria swim in straight lines followed by phases of tumbles, arcs, stops and reversals. A tight control over these phases allows them to direct and adapt movements towards nutrient sources. 

Their intricate pathways of signalling proteins allow them to detect chemical changes in the environment which in turn will affect their run phase. Bacteria must maintain straight trajectories to pick up vital environmental cues and react appropriately. However due to their size and shape, the lengths of their movements are restricted by Brownian motion. 

The rotation friction (fr) co-efficient is the cell’s resistance to being rotated, which is dependent on both cell size and shape. Several models have been suggested for spherical and ellipsoidal cell types. However, despite theoretical modelling, there has been little empirical evidence. 

August’s Paper of the Month, from the Universities of York and Lincoln, focussed on validating the theoretical understanding of how cell size and shape affect bacteria run phases. 

To create bacteria with different aspect ratios they treated E.coli with cephalexin, which was found to elongate the cell. They compared this form to the normal wildtype E.coli. With increasing cell length, they found an increase in flagella along the cell body.
 

Flagella are primarily motile appendages, but also sensory, and are found commonly in the cell bodies of bacteria. 

Using phase contrast microscopy, they then recorded and tracked both the control and elongated group. Samples were imaged while placed on a Linkam PE-100 ZAL system heated to 33°C. 

Their results indicated the elongated cells had shorter runs but longer tumble phases. This finding agreed with the veto model which suggests an increase in flagella increases the average tumble time. 

Although mechanistically different, they also found elongated E.coli performed a run and reverse strategy. This pattern has been described within natural populations of marine and soil bacteria and has been found to be advantageous within these particular niches. 
When asked about the role of the stage, Dr Oscar Guadayol said, “For this kind of study, the ability to perfectly control the environment at the microscale is critical, and thus the PE100 has become an absolutely essential piece of equipment in our everyday exploration of the microbial behaviour.”

Their work experimentally demonstrated long-standing theoretical predictions about how cell elongation may affect the capability of bacteria to swim and to navigate their chemical landscape and how different morphologies can lead to vital changes in motility patterns. 

They are now taking their results one step further and using microfluidic devices with the PE100 to characterize bacterial chemotaxis.
 

A microfluidic chip placed on a Linkam PE100 ZAL system. 

By Tabassum Mujtaba

Guadayol et al., Cell morphology governs directional control in swimming bacteria. Sci Rep| 7: 2061 | DOI:10.1038/s41598-017-01565-y

July's Paper of the Month

A hexagonal ice crystal in the presence of birch pollen molecules. The shape is indicative of ice crystal growth inhibition.

Ice crystal growth through nucleation is an important natural process for atmospheric and cryobiological processes. For biological organisms, surviving sub-freezing temperatures requires tackling intracellular ice formation. Such organisms have evolved antifreeze proteins to inhibit ice crystal growth, thus preserving structural integrity. 

Ice crystals are formed in clouds triggered by ice nucleating particles. Originally it was believed these particles were forms of mineral dust but recent studies have found them to also include biological agents including pollen, bacteria, fungal spores, cellulose and microalgae. 

Active sites are regions on the ice nucleating particles where critical ice embryo formation occurs. These can be proteins or polysaccharides in the cell membrane although studies have found these are still active when separated from their original particles. 

Yet these biological molecules can act as both ice nucleators and ice inhibitors and consequently there has been much desire to further understand the manner in which these molecules interact with ice. The search for such answers may also help to further explain how biological organisms survive extreme climatic conditions.

July’s Paper of the Month comes from the Bielefeld University. They tested for the presence of antifreeze molecules in various types of known ice nucleating boreal pollen. The group conducted their temperature controlled experiment using the Linkam BCS196.

FTIR spectroscopy of the pollen highlighted two polysaccharides with similar chemical structures which differed in size. The larger (>100kD) of the two was responsible for the ice nucleating ability of the pollen while the smaller (<100kD) exhibited ice inhibiting abilities. 
Analysis of IR spectrum suggests the ice inhibiting molecules are either fragments of ice nucleating molecules, or ice nucleating molecules are clusters of smaller ice inhibiting molecules. The group’s results indicate both to have similar molecular moieties. Complementary findings in studies on boreal pollen suggest this may be a mechanism to protect pollen against springtime frosts. 

When asked about the role of the BCS196 stage, Professor Koop said: “For the ice growth inhibition experiments, we have developed an assay which makes use of the BCS196 stage while attached to a brightfield transmission optical microscope. The stage allows for a rapid cooling to about -50 °C in order to produce a film of polycrystalline ice and, subsequently, an accurate and constant hold temperature at -8 °C, during which we determine how the size of the ice crystals changes over several hours and how this is affected by the pollen molecules.”

Their valuable work better helps us to understand the way molecules may be interacting with ice in natural processes. 

By Tabassum Mujtaba

Dreischmeier, K. et al. Boreal pollen contain ice-nucleating as well as ice-binding ‘antifreeze’ polysaccharides. Sci. Rep. 7, 41890; doi: 10.1038/srep41890 (2017).
 

May's Paper of the Month

Blood transfusions are life changing operations needed by many, yet donors – especially for rare blood groups – are hard to come by.  

Medical advancements in the last few decades have seen the average human life expectancy notably increase. However, despite improved medical techniques and procedures, the demand for blood is ever increasing. Donated blood is in short supply and has a limited shelf life while current in-vitro methods of culturing do not provide a sustainable supply suitable for clinical needs. 

May’s paper of the month by Trakarnsanga et al., discovered a method of creating an immortal red blood cell (RBC) supply. Through testing these RBCs have been shown to be molecularly and functionally similar to in vitro cultured RBCs. 

Stem cells are cells which are capable of proliferating into many - and sometimes all - types of cells. Previous in-vitro methods of culturing RBCs used the differentiating abilities of stem cells to produce RBCs from adult peripheral blood or umbilical cord blood stem cells. However, these RBCs have limited proliferation capacity and cells derived from cord blood often show fetal phenotypes. 

Trakarnsanga et al., produced the BEL-A (Bristol Erythroid Line Adult) line which was created through transducing early erythroid cells grown from adult bone marrow stem cells with a plasmid construct. Environmental control maintained these erythroid cells in an indefinitely proliferative state. The cultured cells could then be induced to complete maturation through removal of the inducing factor. The bloodgroup of the cultured RBC matched that of the cell donor while the protein expression profiles of these cells were found to be similar to in-vitro cultured RBCs. 

RBCs must be able to change shape under the stress of mechanical forces without rupturing. Testing this property in the BEL-A line is vital for clinical use. The group used the CSS450 shear stage, Imaging Station and Linkam imaging and control software to test the deformability of the cultured cells. The BEL-A line bound oxygen and had deformability indexes comparable to normal RBCs. 

Transplantation of the BEL-A line into a murine host also proved successful with no difference in survival rate between these mice and mice transplanted with donor RBCs. 

The group have created an immortal RBC line which through testing, matches in-vitro and normal RBCs in all categories tested. The discovery could provide a reliable and suitable blood source for those with rare blood groups and those requiring regular transfusions. Although more work will need to be done before clinical use, the ability to create RBCs through an immortal line could help alleviate the pressure of securing blood donors for patients and could prove life-changing for many.  

By Tabassum Mujtaba

Trakarnsanga, K. et al. An immortalized adult human erythroid line facilitates sustainable and scalable generation of functional red cells. Nat. Commun. 8, 14750 doi: 10.1038/ncomms14750 (2017).
 

April's Paper of the Month

Lithium ion batteries (LIBs) are heavily used in the portable electronics industry due to their low weight and high energy output. Although they are incredibly popular, improvements can be made in terms of capacity and replacing the volatile and flammable organic solvents within the batteries. 

This month’s paper of the month comes from the Warsaw University of Technology. They tested and researched different constituents of LIBs to increase conductivity and capacity of the ionic liquid-lithium salt binary system.  They did so by introducing lithium salt as a Li+ cation glyme solvent. By using the LTS120 system with a Raman spectrometer they could study phase transitions and salt dissociation, giving a better understanding of the conducting mechanism. 

Due to their great conductivity, Ionic liquids (ILs) could be a potential replacement for the dangerous solvents in LIBs. However, there are several issues with their incorporation. Firstly, ILs are produced on a small scale so they are very expensive. Secondly, their high melting points, poor compatibility with electrodes and other electrochemical properties make them less ideal as lithium conducting electrolytes. 

The research group created a new family of ILs to try and improve on the disadvantages of the classic ILs. The ionic salts were mixed with LiTDI salt to create a XMIm+TDI- LiTDI system. This formed a chain shaped [Li(TDI)2]nn- and XMIm+, but this system was found to be a poor conductor of lithium ions. 

Studies from another group found the solvent glyme, when mixed with LiTDI salt, creates a solvated Li(glyme)+ cation and Li polyanion system which is great for ionic conductivity as well as Li cation transference. Both qualities were desired in the Warsaw group’s BMIm+TDI- LiTDI system. 

Karpierz, E. et al. thus incorporated the solvent glyme into their system. Their ternary mixture consisted of an aggregated system of [Li(glyme)]+ cations and [Li(TDI)2]NN- anions dissolved in the ionic liquid BMIm+TDI-. They discovered the order and method of mixing affected the electrochemical properties of their system. They found that by mixing the LiTDI with the glyme first for at least six hours followed by the addition of the ionic liquid, it produces the system with the greatest conductivity.

The group have found a novel method of improving the ionic liquid-lithium salt binary system, which could have great potential application in lithium ion batteries.  

By Tabassum Mujtaba

Karpierz, E. et al. Ternary mixtures of ionic liquids for better salt solubility, conductivity and cation transference number improvement. Sci. Rep. 6, 35587; doi: 10.1038/srep35587 (2016).