Biology subjects

Wood, T. K.

Publications and source records attributed to Wood, T. K..

4 recordsLinked to original sources

bioRxiv2018

Phage Mediate Bacterial Self Recognition

Cells are social, and self-recognition is an important and conserved aspect of group behavior where cells assist kin and antagonize non-kin to conduct group behavior such as foraging for food and biofilm formation. However, the role of the common bacterial cohabitant, phage, in kin recognition, has not been explored. Here we find that a boundary (demarcation line) is formed between different swimming Escherichia coli strains but not between identical clones; hence, motile bacterial cells discriminate between self and non-self. The basis for this self-recognition is a novel, 49 kb, T1-type, lytic phage of the family siphoviridae (named here SW1) that controls formation of the demarcation line by utilizing one of the hosts cryptic prophage proteins, YfdM, to propagate. Critically, SW1 increases the fitness of E. coli K-12 compared to the identical strain that lacks the phage. Therefore, bacteria use phage to recognize kin.

molecular biology↗

bioRxiv2018

Rhamnolipids from Pseudomonas aeruginosa disperse the Biofilms of Sulfate-Reducing Bacteria

Biofilm formation is an important problem for many industries. Desulfovibrio vulgaris is the representative sulfate-reducing bacterium (SRB) which causes metal corrosion in oil wells and drilling equipment, and the corrosion is related to its biofilm formation. Biofilms are extremely difficult to remove since the cells are cemented in a polymer matrix. In an effort to eliminate SRB biofilms, we examined the ability of supernatants from Pseudomonas aeruginosa PA14 to disperse SRB biofilms. We found that the P. aeruginosa supernatants dispersed more than 98% of the biofilm. To determine the genetic basis of this SRB biofilm dispersal, we examined a series of P. aeruginosa mutants and found that mutants rhlA, rhlB, rhlI, and rhlR, defective in rhamnolipids production, had significantly reduced levels of SRB biofilm dispersal. Corroborating these results, purified rhamnolipids dispersed SRB biofilms, and rhamnolipids were detected in the P. aeruginosa supernatants. Hence, P. aeruginosa supernatants disperse SRB biofilms via rhamnolipids. In addition, the supernatants of P. aeruginosa dispersed the SRB biofilms more readily than protease in M9 glucose minimum medium and were also effective against biofilms of Escherichia coli and Bacillus subtilis.

microbiology↗

bioRxiv2018

Single Cell Observations Show Persister Cells Wake Based on Ribosome Content

Since persister cells survive antibiotic treatments through dormancy and resuscitate to reconstitute infections, it is imperative to determine the rate at which these cells revive. Using two sets of Escherichia coli persister cells, those arising naturally at low levels and those generated at high levels by ceasing transcription via rifampicin pretreatment (shown to be bona fide persisters through seven sets of experiments), we used microscopy of single cells to determine that persisters have low levels of antibiotic-corrupting proteins and that their resuscitation is heterogeneous and includes cells that grow immediately. In all, five phenotypes were found for persister cell resuscitation: (i) immediate division, (ii) immediate elongation followed by division, (iii) immediate elongation but no division, (iv) delayed elongation/division, and (v) no growth. In addition, once cell division begins, the growth rate is that of exponential cells. Critically, the greater the ribosome content, the faster the persister cells resuscitate.

microbiology↗

bioRxiv2017

Viable But Non-Culturable Cells Are Persister Cells

Bacteria have two dormant phenotypes: the viable but non-culturable (VBNC) state and the persister state. Both resting stages arise without mutation and both have been linked to chronic infections; however, persister cells revive rapidly whereas the cell population called VBNC is reported to not resuscitate. Here we investigated the relatedness of the two stress-induced phenotypes at the single-cell level by using transmission electron microscopy and fluorescent microscopy to examine cell morphology and by quantifying cell resuscitation. Using the classic starvation conditions to create VBNC cells, we found that the majority of the remaining Escherichia coli population are spherical, have empty cytosol, and fail to resuscitate; however, some of the spherical cells under these classic VBNC-inducing conditions resuscitate immediately (most probably those with dense cytosol). Critically, all the culturable cells became persister cells within 14 days of starvation. We found that the persister cells initially are rodlike, have clear but limited membrane damage, can resuscitate immediately, and gradually become spherical by aging. After 24 h, only rod-shaped persister cells survive, and all the spherical cells lyse. Both cell populations formed under the VBNC-inducing conditions and the persister cells are metabolically inactive. Therefore, the bacterial population consists of dead cells and persister cells in the VBNC-inducing conditions; i.e., the non-lysed particles that do not resuscitate are dead, and the dormant cells that resuscitate are persister cells. Hence, \"VBNC\" and \"persister\" describe the same dormant phenotype.

microbiology↗