Darwin as a botanist

Charles Darwin on his voyage aboard H. M. S. Beagle contracted a mysterious illness that persisted throughout his life. Despite being ill, he continued his writings. He is remembered as the scientist who putforth the theory that species are changing. A species evolves by the accumulation and preservation of successive slight favourable variations, now known as mutations. In his quest to strengthen his theory on the common origin of all life, and evolution by natural selection, he increasingly turned to plants and carried out experiments at his home-cum-laboratory, focusing on phenomena commonly associated with animals namely, movement. In plant roots, seedlings and climbing plants, he described nyctitropism, geotropism, phototropism and circumnutation. Darwin described the sleep movements in plants in which the petiole hangs down and the leaflets press together in the evening.

The adenylyl cyclase Rv2212 modifies the proteome and infectivity of Mycobacterium bovis BCG

All organisms have the capacity to sense and respond to environmental changes. These signals often involve the use of second messengers such as cyclic adenosine monophosphate (cAMP). This second messenger is widely distributed among organisms and coordinates gene expression related with pathogenesis, virulence, and environmental adaptation. Genomic analysis in Mycobacterium tuberculosis has identified 16 adenylyl cyclases (AC) and one phosphodiesterase, which produce and degrade cAMP, respectively. To date, ten AC have been biochemically characterized and only one (Rv0386) has been found to be important during murine infection with M. tuberculosis. Here, we investigated the impact of hsp60-driven Rv2212 gene expression in Mycobacterium bovis Bacillus Calmette-Guerin (BCG) during growth in vitro, and during macrophage and mice infection. We found that hsp60-driven expression of Rv2212 resulted in an increased capacity of replication in murine macrophages but an attenuated phenotype in lungs and spleen when administered intravenously in mice. Furthermore, this strain displayed an altered proteome mainly affecting proteins associated with stress conditions (bfrB, groEL-2, DnaK) that could contribute to the attenuated phenotype observed in mice.