REVIEW | doi:10.20944/preprints202103.0595.v1
Subject: Biology, Anatomy & Morphology Keywords: germination, bacterial cell wall, sporulation, germination, morphology
Online: 24 March 2021 (14:56:55 CET)
A fundamental question in biology is how cell shapes are genetically encoded and enzymatically generated. Prevalent shapes among walled bacteria include spheres and rods. These shapes are chiefly determined by the peptidoglycan (PG) cell wall. Bacterial division results in two daughter cells, whose shapes are predetermined by the mother. This makes it difficult to explore the origin of cell shapes in healthy bacteria. In this review, we argue that the Gram-negative bacterium Myxococcus xanthus is an ideal model for understanding PG assembly and bacterial morphogenesis because it forms rods and spheres at different life stages. Rod-shaped vegetative cells of M. xanthus can thoroughly degrade their PG and form spherical spores. As these spores germinate, cells rebuild their PG and reestablish rod shape without preexisting templates. Such a unique sphere-to-rod transition provides a rare opportunity to visualize de novo PG assembly and rod-like morphogenesis in a well-established model organism.
ARTICLE | doi:10.20944/preprints202012.0511.v1
Subject: Life Sciences, Microbiology Keywords: Antioxidant enzymes; hemibiotroph; reactive oxygen species; host-pathogen interaction; sporulation
Online: 21 December 2020 (11:23:57 CET)
Wheat blast caused by the hemibiotroph fungal pathogen Magnaporthe oryzae Triticum (MoT) pathotype, is a destructive disease of wheat in South America and Bangladesh. Generation of reactive oxygen species (ROS) is one of the defense responses in plants during the infection process by a pathogen. However, empirical evidence on regulation of ROS in wheat and other host and non-host plants towards MoT is limited. This study aimed to determine the susceptibility of some major cereals and weeds of Bangladesh and compare the antioxidant enzyme activities in host and non-host plants in response to artificial inoculation by MoT. Seedlings of wheat, maize, barley and swamp rice grass were susceptible to MoT and produced considerable number of conidia on infected leaves (host). Rice seedlings showed a resistant response in our laboratory conditions (non-host). The activities of ROS-detoxifying enzymes; catalase (CAT), ascorbate peroxidase (APX), Glutathione peroxidase (GPX), Glutathione S-transferase (GST), Peroxidase (POX) increased in all plants after inoculation by MoT with a few exceptions. Interestingly, an early and very high accumulation of CAT was observed within 24 hours of inoculation (hai) in wheat, barley, maize and swamp rice grass while H2O2 concentration was low during that time and immediately after that (24-48 hai). In contrast, an early and high accumulation of H2O2 was observed in rice at 48 hai with little CAT activity only at a late stage. The APX, GST and POD activity was also increased due to the inoculation of MoT at the early stage of infection in rice but were very high at the disease progression stage in wheat, barley, maize and swamp rice grass. GPX activity gradually decreased with the increase of time in rice. Taken together, our results suggest that a robust and late induction of most of the antioxidant enzyme activities occurs in susceptible/host plants whereas an early induction of antioxidant enzyme activities occurs in resistant/ non-host plant but with slow kinetics.