Attractant and repellent induce opposing changes in the four-helix bundle ligand-binding domain of a bacterial chemoreceptor.

Motile bacteria navigate toward favorable conditions and away from unfavorable environments using chemotaxis. Mechanisms of sensing attractants are well understood; however, molecular aspects of how bacteria sense repellents have not been established. Here, we identified malate as a repellent recognized by the MCP2201 chemoreceptor in a bacterium Comamonas testosteroni and showed that it binds to the same site as an attractant citrate. Binding determinants for a repellent and an attractant had only minor differences, and a single amino acid substitution in the binding site inverted the response to malate from a repellent to an attractant. We found that malate and citrate affect the oligomerization state of the ligand-binding domain in opposing way. We also observed opposing effects of repellent and attractant binding on the orientation of an alpha helix connecting the sensory domain to the transmembrane helix. We propose a model to illustrate how positive and negative signals might be generated.

PapA, a peptidoglycan-associated protein, interacts with OmpC and maintains cell envelope integrity.

The bacterial cell envelope is critical to support and maintain cellular life. In Gram-negative bacterial cells, the outer membrane and the peptidoglycan layer are two important parts of the cell envelope and they harbour abundant proteins. Here, we report the identification and characterization of a previously unknown peptidoglycan-associated protein, PapA, from the Gram-negative Comamonas testosteroni. PapA bound peptidoglycan with its C-terminal domain and interacted with the outer-membrane porin OmpC. The PapA-OmpC complex riveted the outer membrane and the peptidoglycan layer, and played a role in maintaining cell envelope integrity. When papA was disrupted, the mutant CNB-1ΔpapA apparently had an outer membrane partly separated from the peptidoglycan layer. Phenotypically, the mutant CNB-1ΔpapA lost chemotactic responses and had longer lag-phase of growth, less flagellation and higher sensitivity to harsh environments. Totally, 1093 functionally unknown PapA homologues were identified from the public NR protein database and they were mainly distributed in Burkholderiales of Betaproteobacteria. Our finding provides a clue that the PapA homologous proteins might function as a rivet to maintain cell envelope integrity in those Gram-negative bacteria.

Bi-needle technique versus transforaminal endoscopic spine system technique for percutaneous endoscopic lumbar discectomy in treating intervertebral disc calcification: a propensity score matched cohort analysis.

OBJECTIVE: The aim of this study was to evaluate the clinical results of a Bi-needle technique and conventional transforaminal endoscopic spine system (TESSYS) technique for percutaneous endoscopic lumbar discectomy (PELD) in treating patients with intervertebral disc calcification (IDC). BACKGROUND: PELD has gained acceptance for treating patients with IDC. The Bi-needle technique was designed to improve the efficiency and safety of PELD. METHOD: Bi-needle and TESSYS group within each cohort were balanced using 1:1 propensity score matching. Finally, 32 patients with IDC treated by Bi-needle technique from December 2015 to September 2017 were enrolled and 25 patients treated by TESSYS technique from the same spine surgery center between January 2013 and October 2017 were enrolled as controls. RESULTS: Propensity score matching generated 22 Bi-needle and 22 TESSYS patients. There were no significant differences in visual analog scale and lumbar Japanese Orthopaedic Association scores between Bi-needle and TESSYS group. Operative time and rate of complications in the Bi-needle was significantly better than the TESSYS group (p < 0.01). CONCLUSIONS: Both surgical methods achieved good clinical outcomes. However, compared with the TESSSY technique, operative time of the Bi-needle technique is shorter, and rate of complications is lower.

Chemotaxis Towards Aromatic Compounds: Insights from Comamonas testosteroni.

Chemotaxis is an important physiological adaptation that allows many motile bacteria to orientate themselves for better niche adaptation. Chemotaxis is best understood in Escherichia coli. Other representative bacteria, such as Rhodobacter sphaeroides, Pseudomonas species, Helicobacter pylori, and Bacillus subtilis, also have been deeply studied and systemically summarized. These bacteria belong to α-, γ-, ε-Proteobacteria, or Firmicutes. However, ß-Proteobacteria, of which many members have been identified as holding chemotactic pathways, lack a summary of chemotaxis. Comamonas testosteroni, belonging to ß-Proteobacteria, grows with and chemotactically responds to a range of aromatic compounds. This paper summarizes the latest research on chemotaxis towards aromatic compounds, mainly from investigations of C. testosteroni and other Comamonas species.

Parapedobacter defluvii sp. nov., isolated from the sewage treatment packing of a coking chemical plant.

Strain WY-1T, a Gram-stain-negative, non-spore-forming, rod-shaped, non-motile bacterium, was isolated from the sewage treatment packing of a coking chemical plant. Strain WY-1T grew over a temperature range of 15-45 °C (optimum, 30-37 °C), a pH range of 5.5-11.0 (optimum, pH 6.5-7.0) and an NaCl concentration range of 0-3 % (w/v; optimum, 0 %). 16S rRNA gene sequence analysis showed that strain WY-1T was closely related to Parapedobacter indicus RK1T with the highest sequence similarity of 96.0 %. The predominant cellular fatty acids of the novel strain were iso-C15 : 0, summed feature 3(C16 : 1ω6c and/or C16 : 1ω7c), iso-C17 : 0 3-OH, iso-C17 : 1ω9c, iso-C15 : 0 3-OH and C16 : 0. The respiratory quinone of the cells was menaquinone 7 (MK-7). The main polar lipid was phosphatidylethanolamine, an unidentified phospholipid, two unidentified aminolipids and two unknown lipids. The G+C content of the DNA was 47.1 mol%. Chemotaxonomic characteristics and phylogenetic analyses revealed that strain WY-1T belonged to the genus Parapedobacter. Strain WY-1T showed a range of phenotypic characteristics that differentiated it from species of the genus Parapedobacter with validly published names, including its assimilation from carbon sources, enzyme activities and having a wider pH range for growth. Based on these results, it is concluded that strain WY-1T represents a novel species of the genus Parapedobacter, for which the name Parapedobacter defluvii sp. nov. is proposed. The type strain is WY-1T (=NBRC 112611T=CGMCC 1.15342T).

Cross Talk between Chemosensory Pathways That Modulate Chemotaxis and Biofilm Formation.

Complex chemosensory systems control multiple biological functions in bacteria, such as chemotaxis, gene regulation, and cell cycle progression. Many species contain more than one chemosensory system per genome, but little is known about their potential interplay. In this study, we reveal cross talk between two chemosensory pathways that modulate chemotaxis and biofilm formation in Comamonas testosteroni We demonstrate that some chemoreceptors that govern chemotaxis also contribute to biofilm formation and these chemoreceptors can physically interact with components of both pathways. Finally, we show that the chemotaxis histidine kinase CheA can phosphorylate not only its cognate response regulator CheY2 but also one of the response regulators from the pathway mediating biofilm formation, FlmD. The phosphoryl group transfer from CheA to CheY2 is much faster than that from CheA to FlmD, which is consistent with chemotaxis being a fast response and biofilm formation being a much slower developmental process. We propose that cross talk between chemosensory pathways may play a role in coordination of complex behaviors in bacteria.IMPORTANCE In many bacteria, two or more homologous chemosensory pathways control several cellular functions, such as motility and gene regulation, in response to changes in the cell's microenvironment. Cross talk between signal transduction systems is poorly understood; while generally it is considered to be undesired, in some instances it might be beneficial for coregulation of complex behaviors. We demonstrate that several receptors from the pathway controlling motility can physically interact with downstream components of the pathway controlling biofilm formation. We further show that a kinase from the pathway controlling motility can also phosphorylate a response regulator from the pathway controlling biofilm formation. We propose that cross talk between two chemosensory pathways might be involved in coordination of two types of cell behavior-chemotaxis and biofilm formation.

Leptin-induced inflammation by activating IL-6 expression contributes to the fibrosis and hypertrophy of ligamentum flavum in lumbar spinal canal stenosis.

The ongoing chronic inflammation and subsequent fibrosis play an important role in ligamentum flavum (LF) fibrosis and hypertrophy in patients with lumbar spinal canal stenosis (LSCS). Leptin is a chronic inflammatory mediator and involved in the fibrotic process in multiple organ systems. The present study aimed to investigate the role of leptin in LF fibrosis and its related regulatory mechanisms. The LF specimens were obtained during the surgery from 12 patients with LSCS (LSCS group) and 12 control patients with lumbar disc herniation (LDH) group. The morphologic changes and fibrosis score of LF were assessed by Hematoxylin and eosin (H&E) and Masson's trichrome staining respectively. The location and expression of leptin in LF tissues were determined. Then, the LF cells were cultured and exposed to recombinant human leptin (rhleptin). Collagen I and III were used as fibrosis markers and IL-6 was used as the inflammatory factor. As a result, the LF thickness and fibrosis score in the LSCS group were significantly higher than those in the LDH group (P<0.05). Leptin was detected in the hypertrophied LF and its expression was substantially increased in the LSCS group and positively correlated with LF thickness and fibrosis score (P<0.05). Moreover, our in vitro experiments revealed that rhleptin treated LF cells elevated the expression of collagen I and III. Finally, leptin administration induced IL-6 expression via nuclear factor-κB (NF-κB) pathway in LF cell (P<0.05). Our study demonstrated novel molecular events for leptin-induced inflammation in LF tissue by promoting IL-6 expression and thus might have potential implications for clarifying the mechanism underlying LF fibrosis and hypertrophy.