Selection of aquatic microbiota exposed to the herbicides flufenacet and metazachlor

Herbicides are important, ubiquitous environmental contaminants, but little is known about their interaction with bacterial aquatic communities. Here, we sampled a protected natural freshwater habitat and characterised its microbiome in interaction with herbicides. We evolved the freshwater microbiomes in a microcosm assay of exposure (28 days) to flufenacet and metazachlor at environmental concentrations of 0.5, 5 and 50 μg L⁻¹. Inhibitory effects of herbicides were exemplarily assessed in cultured bacteria from the same pond (Pseudomonas alcaligenes, Paenibacillus amylolyticus and Microbacterium hominis). Findings were compared to long-term concentrations as provided by local authorities. Here, environmental concentrations reached up to 11 μg L⁻¹ (flufenacet) and 76 μg L⁻¹ (metazachlor). Bacteria were inhibited at minimum inhibitory concentrations far above these values; however, concentrations of 50 μg L⁻¹ of flufenacet resulted in measurable growth impairment. While most herbicide-exposed microcosm assays did not differ from controls, Acidobacteria were selected at high environmental concentrations of herbicides. Alpha-diversity (e.g., taxonomic richness on phylum level) was reduced when aquatic microbiomes were exposed to 50 μg metazachlor or flufenacet. One environmental strain of P. alcaligenes showed resistance to high concentrations of flufenacet (50 g L⁻¹). In total, this study reveals that ecologic imbalance due to herbicide use significantly impacts aquatic microbiomes.     

Scanning electron microscopic investigation of the spermatophore and spermatozoa of the shrimp Farfantepenaeus subtilis (Decapoda: Penaeidae)

Scanning electron microscopy was used to describe the structure of the spermatozoon and spermatophore of Farfantepenaeus subtilis. The spermatophore showed characteristics similar to those of members of the subgenus Farfantepenaeus. This included an extensive glandular epithelium and a lack of a wing. The sperm mass, which was distributed at the periphery of the spermatophore, was surrounded by a large amount of acellular material. The spermatozoon has a spherical main body and a well-defined acrosomal region with a single spike, which was bent in some cells. The immotile sperm cells have an average length of 7.1?±?0.6?μm. Information on sperm location within the spermatophore will assist in the efficient extraction of the sperm mass during dissection.     

Presynaptic activity and protein turnover are correlated at the single-synapse level

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Antibiotic resistance and persistence—Implications for human health and treatment perspectives

Antimicrobial resistance (AMR) and persistence are associated with an elevated risk of treatment failure and relapsing infections. They are thus important drivers of increased morbidity and mortality rates resulting in growing healthcare costs. Antibiotic resistance is readily identifiable with standard microbiological assays, and the threat imposed by antibiotic resistance has been well recognized. Measures aiming to reduce resistance development and spreading of resistant bacteria are being enforced. However, the phenomenon of bacteria surviving antibiotic exposure despite being fully susceptible, so‐called antibiotic persistence, is still largely underestimated. In contrast to antibiotic resistance, antibiotic persistence is difficult to measure and therefore often missed, potentially leading to treatment failures. In this review, we focus on bacterial mechanisms allowing evasion of antibiotic killing and discuss their implications on human health. We describe the relationship between antibiotic persistence and bacterial heterogeneity and discuss recent studies that link bacterial persistence and tolerance with the evolution of antibiotic resistance. Finally, we review persister detection methods, novel strategies aiming at eradicating bacterial persisters and the latest advances in the development of new antibiotics.     

Benzodiazepine receptors': Correlation with pharmacological responses in living animals

The data relating the pharmacological activities of benzodiazepines to $\text{in vivo}$ occupancy of their receptor sites is reviewed, in the light of the complexity of evaluating pharmacodynamic parameters in living animals. Methodological problems in the measurement of $\text{in vivo}$ receptor occupancy and species differences in benzodiazepine metabolism are considered in detail.     

Gαs directly drives PDZ-RhoGEF signaling to Cdc42

Gα proteins promote dynamic adjustments of cell shape directed by actin-cytoskeleton reorganization via their respective RhoGEF effectors. For example, Gα₁₃ binding to the RGS-homology (RH) domains of several RH-RhoGEFs allosterically activates these proteins, causing them to expose their catalytic Dbl-homology (DH)/pleckstrin-homology (PH) regions, which triggers downstream signals. However, whether additional Gα proteins might directly regulate the RH-RhoGEFs was not known. To explore this question, we first examined the morphological effects of expressing shortened RH-RhoGEF DH/PH constructs of p115RhoGEF/ARHGEF1, PDZ-RhoGEF (PRG)/ARHGEF11, and LARG/ARHGEF12. As expected, the three constructs promoted cell contraction and activated RhoA, known to be downstream of Gα₁₃. Intriguingly, PRG DH/PH also induced filopodia-like cell protrusions and activated Cdc42. This pathway was stimulated by constitutively active Gα_s (Gα_sQ227L), which enabled endogenous PRG to gain affinity for Cdc42. A chemogenetic approach revealed that signaling by G_s-coupled receptors, but not by those coupled to G_i or G_q, enabled PRG to bind Cdc42. This receptor-dependent effect, as well as CREB phosphorylation, was blocked by a construct derived from the PRG:Gα_s-binding region, PRG-linker. Active Gα_s interacted with isolated PRG DH and PH domains and their linker. In addition, this construct interfered with Gα_sQ227L''s ability to guide PRG''s interaction with Cdc42. Endogenous G_s-coupled prostaglandin receptors stimulated PRG binding to membrane fractions and activated signaling to PKA, and this canonical endogenous pathway was attenuated by PRG-linker. Altogether, our results demonstrate that active Gα_s can recognize PRG as a novel effector directing its DH/PH catalytic module to gain affinity for Cdc42.