The Dynamics of Mycoplasma gallisepticum Nucleoid Structure at the Exponential and Stationary Growth Phases

Abstract

The structure and dynamics of bacterial nucleoids play important roles in regulating gene expression. Bacteria of class Mollicutes and, in particular, mycoplasmas feature extremely reduced genomes. They lack multiple structural proteins of the nucleoid, as well as regulators of gene expression. We studied the organization of Mycoplasma gallisepticum nucleoids in the stationary and exponential growth phases at the structural and protein levels. The growth phase transition results in the structural reorganization of M. gallisepticum nucleoid. In particular, it undergoes condensation and changes in the protein content. The observed changes corroborate with the previously identified global rearrangement of the transcriptional landscape in this bacterium during the growth phase transition. In addition, we identified that the glycolytic enzyme enolase functions as a nucleoid structural protein in this bacterium. It is capable of non-specific DNA binding and can form fibril-like complexes with DNA.

Unraveling the adaptive strategies of Mycoplasma hominis through proteogenomic profiling of clinical isolates

“…Alongside, the increase in abundance of ribosomal proteins - components of both large and small ribosomal subunits, featured in all isolates ( Supplementary Figure S6 ), may result from incomplete synchronization between cell division and other cellular processes. However, there is increasing evidence that ribosomal proteins, besides their canonical functions, may serve other roles, such as acting as nucleoid-binding proteins ( Fisunov et al., 2021 ) or functioning as ligands for ribosome switching ( Deiorio-Haggar et al., 2013 ). It cannot be excluded that the upregulation of ribosomal proteins in all isolates is somehow related to the adaptation of M. hominis in the host organism.…”

“…Ribosomal proteins are known to perform non-canonical functions. Fisunov et al suggested that ribosomal proteins non-specifically bind DNA and participate as nucleoid-associated proteins, regulating nucleoid architecture, which in turn affects gene expression regulation (Fisunov et al, 2021). Since Mycoplasmas have a minimal number of known transcription factors, gene regulation may be carried out by other mechanisms, in particular by changing the structure of nucleoid.…”

Gene Silencing through CRISPR Interference in Mycoplasmas

“…In order to ensure the optimal length (8 nt) of the spacer between the Shine-Dalgarno (SD) box and AUG start codon, we used a primer (dCas9_mut_1a_F) with a non-complementary 5 -end. The selected sequences of the promoter and SD-box were tested in reporter constructs in our previous study [5]. The resulting plasmid was annotated as pRLM5L2-dcas9 (Figure 1C).…”

“…Many of these genes are often unique to mycoplasmas. At the same time, genes kept in genome-reduced bacteria can either have broader functions like Eno [5,6], GAPDH [7], EF-Tu [8] or represent a new alternative group of genes that are involved in vital processes. A high proportion of essential genes is shown for mycoplasmas [9,10].…”

Spatiotemporal Coupling of DNA Supercoiling and Genomic Sequence Organization—A Timing Chain for the Bacterial Growth Cycle?

“…The bacterial growth cycle appears as an intrinsically ordered process following a “programmed” as it were, passage of the population through successive, physiologically distinct states or “growth phases” associated with transitions in nucleoid structure [ 35 , 113 , 114 , 115 ]. Notwithstanding the existence of evolutionarily pre-programmed phase transitions in nucleoid structure, this sequential order during the bacterial growth cycle could also be produced by the continuous adjustment of the physiological state to changing growth environments and thus, be largely determined, or better to say, triggered by the latter.…”