Carbon isotope composition of canopy leaves in a tropical forest in Panama throughout a seasonal cycle

The seasonal variation in δ13C values was measured in leaves from 17 upper canopy, five mid-canopy and in four gap tree species, as well as in five epiphyte and five vine species, in a seasonally dry lowland tropical forest at Parque Natural Metropolitano near Panama City, Republic of Panama. No seasonal variation was detected in the δ13C values of mature exposed leaves from either the upper or mid-canopy. However, canopy position did influence the δ13C value. The mean isotopic composition of leaves from the mid-canopy was more negative than that of the upper canopy throughout the year. The δ13C value was also influenced by leaf development, with juvenile leaves on average 1.5‰ less negative than mature leaves. The five epiphyte species exhibited 13C values that were typical of crassulacean acid metabolism (CAM). Codonanthe uleana, with isotopic values of .19.9 to .22.1‰, is only the second species in the Gesneriaceae reported to express CAM, whereas values between .14.6 and .22.0‰ indicate that Peperomia macrostachya can exhibit different degrees of CAM. The isotopic composition of exposed mature leaves from the vines showed little interspecific variation and was similar to the upper-canopy leaves of the trees

Antibiotics in the clinical pipeline in 2013

The continued emergence of multi-drug-resistant bacteria is a major public health concern. The identification and development of new antibiotics, especially those with new modes of action, is imperative to help treat these infections. This review lists the 22 new antibiotics launched since 2000 and details the two first-in-class antibiotics, fidaxomicin (1) and bedaquiline (2), launched in 2011 and 2012, respectively. The development status, mode of action, spectra of activity, historical discovery and origin of the drug pharmacophore (natural product, natural product derived, synthetic or protein/mammalian peptide) of the 49 compounds and 6 β-lactamase/β-lactam combinations in active clinical development are discussed, as well as compounds that have been discontinued from clinical development since 2011. New antibacterial pharmacophore templates are also reviewed and analyzed