Whereas standard transmission electron microscopy studies are unable to preserve the native state of chemically reactive and beam-sensitive battery materials after operation, such materials remain pristine at cryogenic conditions. It is then possible to atomically resolve individual lithium metal atoms and their interface with the solid electrolyte interphase (SEI). We observe that dendrites in carbonate-based electrolytes grow along the <111> (preferred), <110>, or <211> directions as faceted, single-crystalline nanowires. These growth directions can change at kinks with no observable crystallographic defect. Furthermore, we reveal distinct SEI nanostructures formed in different electrolytes.

Anaerobic cellulolytic bacteria are thought to adhere to cellulose via several mechanisms, including production of a glycocalyx containing extracellular polymeric substances (EPS). As the compositions and structures of these glycocalyces have not been elucidated, variable-pressure scanning electron microscopy (VP-SEM) and chemical analysis were used to characterize the glycocalyx of the ruminal bacterium Ruminococcus albus strain 7. VP-SEM revealed that growth of this strain was accompanied by the formation of thin cellular extensions that allowed the bacterium to adhere to cellulose, followed by formation of a ramifying network that interconnected individual cells to one another and to the unraveling cellulose microfibrils.

Pseudomonas aeruginosa (Pa) and Candida albicans (Ca) are major bacterial and fungal pathogens in immunocompromised hosts, and notably in the airways of cystic fibrosis patients. The bacteriophages of Pa physically alter biofilms, and were recently shown to inhibit the biofilms of Aspergillus fumigatus. To understand the range of this viral-fungal interaction, we studied Pa phages Pf4 and Pf1, and their interactions with Ca biofilm formation and preformed Ca biofilm. Both forms of Ca biofilm development, as well as planktonic Ca growth, were inhibited by either phage. The inhibition of biofilm was reversed by the addition of iron, suggesting that the mechanism of phage action on Ca involves denial of iron. Birefringence studies on added phage showed an ordered structure of binding to Ca. Electron microscopic observations indicated phage aggregation in the biofilm extracellular matrix. Bacteriophage-fungal interactions may be a general feature with several pathogens in the fungal kingdom.

Controlling the transition from a multicellular motile state to a sessile biofilm is an important eco-physiological decision for most prokaryotes, including cyanobacteria. Photosynthetic and bio geochemically significant cyanobacterium Synechocystis sp. PCC6803 (Syn6803) uses Type IV pili (TFP) for surface-associated motility and light-directed phototaxis. We report the identification of a novel Chaperone-Usher (CU) system in Syn6803 that regulate secretion of minor pilins as a means of stabilizing TFP morphology. These secreted minor-pilins aid in modifying TFP morphology to suit the adhesion state by forming cell to surface contacts when motility is not required. This morphotype is structurally distinct from TFP assembled during motile phase. We further demonstrate by examining mutants lacking either the CU system or the minor-pilins, which produce aberrant TFP, that are morphologically and functionally distinct from wild-type (WT). Thus, here we report that in Syn6803, CU system work independent of TFP biogenesis machinery unlike reported for other pathogenic bacterial systems and contributes to provide multifunctional plasticity to TFP. cAMP levels play an important role in controlling this switch. This phenotypic plasticity exhibited by the TFP, in response to cAMP levels would allow cells and cellular communities to adapt to rapidly fluctuating environments by dynamically transitioning between motile and sessile states.Significance of this workHow cyanobacterial communities cope with fluctuating or extreme environments is crucial in understanding their role in global carbon and nitrogen cycles. This work addresses the key question: how do cyanobacteria modulate external appendages, called Type IV pili, to effectively switch between motile and sessile biofilm states? We demonstrate that cells transition between forming strong cell-surface interactions indispensable for biofilm formation to forming cell-cell interactions that allow for coordinated movement crucial for social motility by functional/ structural modification of same TFP appendage. The second messenger, cAMP and a Chaperone-Usher secretion are indispensible to achieve these structural modifications of TFP and control the complex phenotypic transition. We have uncovered a strategy that Syn6803 has evolved to deal with molecular decision-making under uncertainty, which we call phenotypic plasticity. Here we demonstrate how a single motility appendage can be structurally modified to attain two antagonistic functions in order to meet the fluctuating environmental demands.

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