Biology subjects

Randich, A. M.

Publications and source records attributed to Randich, A. M..

3 recordsLinked to original sources

bioRxiv2026

Emended description of the genus Henriciella: morphological and phylogenetic analysis identifies two subgenera with different reproductive strategies

Henriciella is the only genus with reported non-prosthecate members in the family Hyphomonadaceae, a large group of dimorphic prosthecate bacteria. Using type strains, we reinvestigated growth in media shown to support prosthecate morphotypes in marine caulobacters. We report that Marine Broth (MB) and Peptone Yeast Extract (PYE)-derived media supported prosthecate populations for all Henriciella species. Surprisingly, we observed that H. aquimarina, H. mobilis, and H. pelagia reproduce by tip budding whereas H. marina and H. liltoralis reproduce by asymmetric binary fission. These two observed reproductive strategies resemble those characterized for the model prosthecate bacteria Hyphomonas neptunium and Caulobacter crescentus. Phylogenomic analysis indicates that H. marina, H. litoralis, H. algicola, and H. barbarensis form a monophyletic subgenus that reproduces by asymmetric binary fission. We propose genus and species emendations that correct the record on this fascinating genus.

microbiology↗

bioRxiv2025

Ancient Truncated FtsZ Paralogs Likely Tune Cell Division in Hyphomicrobiales

Bacterial cell division is a well conserved, tightly regulated process that allows the separation of two viable daughter cells. In most bacteria, the proteins that drive division, termed the divisome, are recruited to mid-cell by FtsZ after it polymerizes to form the Z- ring. Interestingly, FtsZ has undergone several independent duplication events across the bacterial kingdom. We identified FtsZ GTPase protein sequences across alphaproteobacterial genomes, from representative genera for each family, and observed numerous ftsZ duplications in the order Hyphomicrobiales. Hidden Markov Modeling (HMM) supported the maintenance of two distinct lineages of FtsZ GTPase duplications among three families. The Nitrobacteraceae duplication, occurring in only the genus Bradyrhizobium, exhibits a different substitution pattern from that shared by the Phyllobacteraceae and Rhizobiaceae families. Within the Rhizobiaceae lineage, Agrobacterium tumefaciens contains three paralogs of FtsZ including the essential FtsZAT, and paralogs FtsZ1, and FtsZ3. In A. tumefaciens, we show that FtsZ1, but not FtsZ3, inhibits cell division when overexpressed. A hyperactive allele of ftsW partially protected against overexpression of ftsZ1 suggesting that FtsZ1 may inhibit proper regulation of septal peptidoglycan biosynthesis during cell division. Overall, these observations suggest that maintenance of FtsZ paralogs in some bacteria which may fine tune the division process. Article SummaryGene duplication drives evolutionary innovation by providing raw genetic material and allowing microbes to acquire novel functions. Here, we explore the duplication of a gene encoding the essential cell division protein FtsZ in the Hyphomicrobiales and find that the duplication is primarily conserved in genera that interact with plant hosts. In A. tumefaciens FtsZ1 is not essential for cell division; however, overexpression of FtsZ1 inhibited cell division suggesting it may have a regulatory role during this essential process. This observation highlights the key role for gene duplication in the modulation of complex processes in bacteria.

microbiology↗

bioRxiv2018

Beating Swords into Ploughshares: Domestication of a Phage Lysin for Housekeeping Function

Temperate phages constitute a potentially beneficial genetic reservoir for bacterial innovation despite being selfish entities encoding an infection cycle inherently at odds with bacterial fitness. These phages integrate their genomes into the bacterial host during infection, donating new, but deleterious, genetic material: the phage genome encodes toxic genes, such as lysins, that kill the bacterium during the phage infection cycle. Remarkably, some bacteria have exploited the destructive properties of phage genes for their own benefit by co-opting them as toxins for functions related to bacterial warfare, virulence, and secretion. However, do toxic phage genes ever become raw material for functional innovation? Here we report on a toxic phage gene whose product has lost its toxicity and has become a domain of a core cellular factor, SpmX, throughout the bacterial order Caulobacterales. Using a combination of phylogenetics, bioinformatics, structural biology, cell biology, and biochemistry, we have investigated the origin and function of SpmX and determined that its occurrence is the result of the detoxification of a phage peptidoglycan hydrolase gene. We show that the retained, attenuated activity of the phage-derived domain plays an important role in proper cell morphology and developmental regulation in representatives of this large bacterial clade. To our knowledge, this is the first observation of phage gene domestication in which a toxic phage gene has been co-opted for a housekeeping function.

microbiology↗