No abstract

The treatment of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) is a challenge worldwide. In our search for novel antimicrobial agents against MRSA, we constructed a chimeric lysin (named as ClyH) by fusing the catalytic domain of Ply187 (Pc) with the non-SH3b-like cell wall binding domain of phiNM3 lysin. Herein, the antimicrobial activity of ClyH against MRSA strains in vitro and in vivo was studied. Our results showed that ClyH could kill all of the tested clinical isolates of MRSA with higher efficacy than lysostaphin as well as its parental enzyme. The MICs of ClyH against clinical S. aureus strains were found to be as low as 0.05 to 1.61 mg/liter. In a mouse model, a single intraperitoneal administration of ClyH protected mice from death caused by MRSA, without obvious harmful effects. The present data suggest that ClyH has the potential to be an alternative therapeutic agent for the treatment of infections caused by MRSA.

Rusted root (also known as rusty root) of ginseng (Panax quinquefolius) was first described over 70 years ago, but the causal agent has not been clearly established. The disease is characterized by slightly raised reddish-brown to black root lesions of varying size. The lesions, regardless of size, remain superficial; however, peridermal tissue is ruptured and sloughed off, giving the root a scabbed appearance. Culture-independent techniques were used to demonstrate that a fungal internal transcribed spacer (ITS) region DNA fragment was strongly associated with diseased but not healthy root tissue. The fragment ( approximately 650 bp in length) was cloned. Restriction enzyme digests of cloned DNA indicated that the 650-bp fragment represented a single taxon. BLAST analysis following sequencing of the fragment found that the nearest matches in GenBank were anamorphic genera associated with discomycetes, in particular Rhexocercosporidium spp. This putative identification was supported further by isolating fungi from diseased tissue using a semiselective agar medium. With this procedure, a Rhexocercosporidium-like fungus was isolated; DNA extracted from fungal cultures and amplified using ITS oligonucleotide primers was found to be identical to similarly amplified DNA from the 650-bp bands. However, the isolates were distinct, with respect to growth rate on agar media and ITS sequence, from Rhexocercosporidium carotae, the only described species in this genus. The ability to reproduce symptoms on ginseng roots was confirmed in pathogenicity tests. Oligonucleotide primers based on ITS sequences were designed to amplify DNA of Rhexocercosporidium spp. Polymerase chain reaction assays on DNA extracted from naturally infected root tissue showed that the fungus was present in nearly all symptomatic roots but was infrequent in healthy-appearing roots. The most probable cause of rusted root of ginseng is a previously undescribed species of Rhexocercosporidium.

Reproductive behaviors have manifold consequences on evolutionary processes. Here, we explore mechanisms underlying female reproductive choice in the nematode Caenorhabditis elegans, a species in which females have evolved the ability to produce their own self-fertilizing sperm, thereby allowing these "hermaphrodites" the strategic choice to self-reproduce or outcross with males. We report that hermaphrodites of the wild-type laboratory reference strain N2 favor self-reproduction, whereas a wild isolate CB4856 (HW) favors outcrossing. To characterize underlying neural mechanisms, we show that N2 hermaphrodites deficient in mechanosensation or chemosensation (e.g., mec-3 and osm-6 mutants) exhibit high mating frequency, implicating hermaphrodite perception of males as a requirement for low mating frequency. Within chemosensory networks, we find opposing roles for different sets of neurons that express the cyclic GMP-gated nucleotide channel, suggesting both positive and negative sensory-mediated regulation of hermaphrodite mating frequency. We also show that the ability to self-reproduce negatively regulates hermaphrodite mating. To map genetic variation, we created recombinant inbred lines and identified two QTL that explain a large portion of N2 × HW variation in hermaphrodite mating frequency. Intriguingly, we further show that ∼40 wild isolates representing C. elegans global diversity exhibit extensive and continuous variation in hermaphrodite reproductive outcome. Together, our findings demonstrate that C. elegans hermaphrodites actively regulate the choice between selfing and crossing, highlight the existence of natural variation in hermaphrodite choice, and lay the groundwork for molecular dissection of this evolutionarily important trait.