STUDY OF TECHNICAL CELLULOSE AS A MATRIX-SORBENT TO DEVELOP EXPRESS ANALYTIC SYSTEM FOR WATER SAFETY CONTROL

The study presented by the authors is devoted to the study of the properties and the possibility of using technical cellulose from non-wood plant raw materials as a solid-phase matrix to obtain solid-phase reactive indicator systems by the following methods: synthesis method on the base of a hetarylformazane immobilized on a cellulose matrix and development of analytical systems based on preconcentration of the determined metal ion by a matrix with subsequent its «revealing» by the formazan («revealing» method). The article focuses on determination of optimal combinations of chromogenic organic reagents (hetarylformazanes) and cellulose-based matrices for developing solid-phase reaction-based indicator systems. Adsorption features of formazan reagents onto cellulose matrices was studied. It has been established the relation between the reagent molecule structure, composition of cellulose matrix and analytical properties of the test-systems synthesized to determine metal ions. Different approaches were developed and applied to reveal the visually observable and easily measured effect due to cellulose properties as well as properties of hetarylformazanes fixed on the surface of the matrix. This fact allows to control sensitivity and selectivity of solid-phase reactive indicator systems for water quality assessment.

Extracellular DNA and Outer Membrane Vesicles contribute to P. fluorescens SBW25 air-liquid interface biofilms.

<p>Outer membrane vesicles (OMVs) and extracellular DNA (eDNA) are important for biofilm formation for many bacteria. OMVs are a perfect transport system to deliver biofilm-related components including eDNA beyond the boundaries of cells, and eDNA itself is an important structural component of biofilms as well as enabling horizontal gene transfer and local adaptation. Both OMVs and eDNA are found in the biofilms produced by the opportunistic human pathogen P. aeruginosa and the plant pathogen P. syringae, but as yet, they have not been reported in the cellulose matrix-based biofilms produced by the related model rhizosphere bacterium Pseudomonas fluorescens SBW25.</p> <p>In this work we have gone back to re-assess the complexity of SBW25 biofilms by looking for evidence of OMVs and eDNA associated with biofilm–formation. OMVs were first imaged by SEM and LC-MC analysis used to identify 51 biofilm matrix-associated proteins of which 12 were also identified in biofilm OMVs. Interestingly, only 5 proteins were identified in both biofilm matrix and OMV samples, but not in planktonic OMVs, suggesting that these may be biofilm-specific components.  </p> <p>We also observed eDNA by CLSM in both the weak and poorly-attached Viscous Mass (VM) and robust and well-attached Wrinkly Spreader (WS) air-liquid (A-L) interface biofilms produced by wild-type SBW25 and the Wrinkly Spreader mutant. The eDNA fraction could be precipitated from biofilm cell-free supernatant samples which demonstrated that WS biofilms had two-fold–higher levels than VM biofilms. DNAse treatment effected the development of both types of biofilm and reduced the strength and attachment levels when added to mature VM and WS biofilms. Testing with exogenous DNA suggests that high molecular weight (HMW) DNA is involved in both strength and attachment, perhaps by surface conditioning and interactions with the primary cellulose matrix common to both biofilms. HMW eDNA could be isolated directly from biofilm supernatants whereas two different HMW size fractions could be isolated from OMVs, presumably, from the outer OMV surface because DNAse treatment led to a substantially reduced DNA signal. This suggest that eDNA persistence and degradation in SBW25 biofilms is complex and eDNA fractions may play different roles in biofilm development, protection and adaptation.</p>

Living materials with programmable functionalities grown from engineered microbial co-cultures

ABSTRACTBiological systems assemble tissues and structures with advanced properties in ways that cannot be achieved by man-made materials. Living materials self-assemble under mild conditions, are autonomously patterned, can self-repair and sense and respond to their environment. Inspired by this, the field of engineered living materials (ELMs) aims to use genetically-engineered organisms to generate novel materials. Bacterial cellulose (BC) is a biological material with impressive physical properties and low cost of production that is an attractive substrate for ELMs. Inspired by how plants build materials from tissues with specialist cells we here developed a system for making novel BC-based ELMs by addition of engineered yeast programmed to add functional traits to a cellulose matrix. This is achieved via a synthetic ‘symbiotic culture of bacteria and yeast’ (Syn-SCOBY) approach that uses a stable co-culture of Saccharomyces cerevisiae with BC-producing Komagataeibacter rhaeticus bacetria. Our Syn-SCOBY approach allows inoculation of engineered cells into simple growth media, and under mild conditions materials self-assemble with genetically-programmable functional properties in days. We show that co-cultured yeast can be engineered to secrete enzymes into BC, generating autonomously grown catalytic materials and enabling DNA-encoded modification of BC bulk material properties. We further developed a method for incorporating S. cerevisiae within the growing cellulose matrix, creating living materials that can sense chemical and optical inputs. This enabled growth of living sensor materials that can detect and respond to environmental pollutants, as well as living films that grow images based on projected patterns. This novel and robust Syn-SCOBY system empowers the sustainable production of BC-based ELMs.