Biology subjects

Garcia, P. S.

Publications and source records attributed to Garcia, P. S..

3 recordsLinked to original sources

bioRxiv2018

RocS drives chromosome segregation and nucleoid occlusion in Streptococcus pneumoniae

Segregation of replicated chromosomes in bacteria is poorly understood outside some prominent model strains and even less is known about how it is coordinated with other cellular processes. Here we report that RocS is crucial for chromosome segregation in the opportunistic human pathogen Streptococcus pneumoniae. RocS is membrane-bound and interacts both with DNA and the chromosome partitioning protein ParB to properly segregate the origin of replication region to new daughter cells. In addition, we show that RocS interacts with the tyrosine-autokinase CpsD required for polysaccharide capsule biogenesis, which is crucial for S. pneumoniaes ability to prevent host immune detection. Altering the RocS-CpsD interaction drastically hinders chromosome partitioning and cell division. Altogether, this work reveals that RocS is the cornerstone of an atypical nucleoid occlusion system ensuring proper cell division in coordination with the biogenesis of a protective capsular layer.

microbiology↗

bioRxiv2018

Faster emergence behavior from ketamine/xylazine anesthesia with atipamezole versus yohimbine

Recent interest in reversal of the hypnotic effects of anesthesia has mainly focused on overcoming a surge in GABA-mediated inhibitory signaling through activation of subcortical arousal circuits or antagonizing GABA receptors. Here we examine the reversal of anesthesia produced from non-GABA agents ketamine/xylazine and the effects of antagonists of adrenoreceptors. These antagonists vary in selectivity and produce temporally unique waking behavior post-anesthesia. We compared two antagonists with differential selectivity for 1-vs. 2-receptors, yohimbine (YOH, 1:40 selectivity) and atipamezole (ATI, 1:8500). Adult mice received intraperitoneal injections of either YOH (4.3 mg/kg), ATI (0.4 mg/kg), or saline after achieving sustained loss of righting following injection of ketamine/xylazine (ketamine: 65.0 mg/kg; xylazine: 9.9 mg/kg). Behaviors indicative of the post-anesthesia, re-animation sequence were carefully monitored and the timing of each behavior relative to anesthesia induction was compared. Both YOH and ATI hastened behaviors indicative of emergence, but ATI was faster than YOH to produce certain behaviors, including whisker movement (YOH: 21.9{+/-}1.5 min, ATI: 17.5{+/-}0.5 min, p=0.004) and return of righting reflex (RORR) (YOH: 40.6{+/-}8.8 min, ATI: 26.0{+/-}1.2 min, p<0.001). Interestingly, although YOH administration hastened early behavioral markers of emergence relative to saline (whisking), the completion of the emergence sequence (time from first marker to appearance of RORR) was delayed with YOH. We attribute this effect to antagonism of 1 receptors by yohimbine. Also notable was the failure of either antagonist to hasten the re-establishment of coordinated motor behavior (e.g., attempts to remove adhesive tape on the forepaw placed during anesthesia) relative to the end of emergence (RORR). In total, our work suggests that in addition to pharmacokinetic effects, re-establishment of normal waking behaviors after anesthesia involves neuronal circuits dependent on time and/or activity.

neuroscience↗

bioRxiv2018

Identification of a novel subfamily of bacterial AAT-fold basic amino acid decarboxylases and functional characterization of its first representative: Pseudomonas aeruginosa LdcA

Polyamines are small amino-acid derived polycations capable of binding negatively charged macromolecules. Bacterial polyamines are structurally and functionally diverse, and are mainly produced biosynthetically by PLP-dependent amino acid decarboxylases referred to as LAOdcs (Lysine-Arginine-Ornithine decarboxylases). In a phylogenetically limited group of bacteria, LAOdcs are also induced in response to acid stress. Here, we performed an exhaustive phylogenetic analysis of the AAT-fold LAOdcs which showcased the ancestral nature of their short forms in Cyanobacteria and Firmicutes, and emergence of distinct subfamilies of long LAOdcs in Proteobacteria. We identified a novel subfamily of lysine decarboxylases, LdcA, ancestral in Betaproteobacteria and Pseudomortadaceae {Gammaproteobacteria). We analyzed the expression of LdcA from Pseudomonas aeruginosa, and uncovered its role, intimately linked to cadaverine production, in promoting growth and reducing persistence of this multidrug resistant human pathogen during carbenicillin treatment. Finally, we documented a certain redundancy in the function of the three main polyamines - cadaverine, putrescine and spermidine - in P. aeruginosa by demonstrating the link between their intracellular level, as well as the capacity of putrescine and spermidine to complement the growth phenotype of the IdcA mutant.

microbiology↗