Hypercyst Mutants in Rhodospirillum centenum Identify Regulatory Loci Involved in Cyst Cell Differentiation

Abstract

Rhodospirillum centenum is a purple photosynthetic bacterium that forms resting cyst cells when starved for nutrients. In this study, we demonstrate that chalcone synthase gene (chsA) expression is developmentally regulated, with expression of chsA increasing up to 86-fold upon induction of the cyst developmental cycle. Screening for mini-Tn5-induced mutants that exhibit elevated chsA::lacZ expression has led to the isolation of a set of R. centenum mutants that display increased chsA gene expression concomitant with constitutive induction of the cyst developmental cycle. These "hypercyst" mutants have lost the ability to regulate cyst cell formation in response to nutrient availability. Sequence analysis indicates that the mini-Tn5-disrupted genes code for a variety of factors, including metabolic enzymes and a large set of potential regulatory factors, including four gene products with homology to histidine sensor kinases and three with homology to response regulators. Several of the disrupted genes also have sequence similarity to che-like signal transduction components.

Isolation, Morphological and Cultural Characterisation of Azospirillum Isolated from Rhizospheric Soils of Various Non-Leguminous Crops of Ranchi Having Acidic pH

“…All the isolates were having capability of forming microcysts. Transition into cyst-like cells were observed in older cultures of Azospirillum was reported by Berlman (2004). Extracellular capsule was present in all 54 isolates which is in confirmity with reports of Madi et al, (1988).…”

Ligand-Binding PAS Domains in a Genomic, Cellular, and Structural Context

“…Multidomain proteins encoding a PYP domain have been discovered in a number of other bacteria (111), the most well-characterized being Ppr of Rhodospirillum centenum . This hybrid photoreceptor encodes a blue-absorbing PYP domain coupled to a red-absorbing bacteriophytochrome domain (56), and regulates the development of starvation-resistant cysts (9). Recent characterization of Ppr from Rhodocista centenaria provides evidence that this hybrid photoreceptor also functions in the chemotaxis signaling pathway (65).…”

Genome Sequence ofAzotobacter vinelandii, an Obligate Aerobe Specialized To Support Diverse Anaerobic Metabolic Processes

“…Only a few bacterial species have been observed to make cysts. Initial studies of cyst formation in Rhodospirillum centenum and Azospirillum brasiliense identified a few genes (4,88) that are involved in the regulation of encystment in these bacteria. Genes similar to these regulators, however, have not been found in the A. vinelandii genome.…”