Formation of unique T-shape budding and differential impacts of low surface water on Bacillus mycoides rhizoidal colony.

Bacillus mycoides Ko01 strain grows rapidly and forms extensive rhizoidal colonies on hard agar despite limited surface water availability. The agar concentrations affect the handedness of the colonies as well as other colony architectures. In this study, we found that the local curvature of cell chains in the developing colonies did not vary based on the agar concentration, while concentration does affect the handedness of chirality at the macroscale. This result suggests independence between the microscale filament curvature and macroscale colony chirality. In addition, we discovered a novel microscopic property of cells that has not been observed before: T-shaped budding under extremely low surface water availability conditions. We propose that this feature gives rise to chaotic colony morphology. Together with bundling of chains, cells form a unique set of spatial arrangements under different surface water availability. These properties appear to impact the structural features of thick tendrils, and thereby the overall morphology of colonies. Our study provides additional insights as to how bacteria proliferate, spread, and develop macroscale colony architecture under water-limited conditions.

Cellular Memory of HipA-Induced Growth Arrest: The Length of Cell Growth Arrest Becomes Shorter for Each Successive Induction.

Toxin-antitoxin (TA) systems are genetic modules found commonly in bacterial genomes. HipA is a toxin protein encoded from the hipBA TA system in the genome of Escherichia coli. Ectopic expression of hipA induces cell growth arrest. Unlike the cell growth arrest caused by other TA toxins, cells resume growth from the HipA-induced cell growth arrest phase after a defined period of time. In this article, we describe the change in the length of growth arrest while cells undergo repeated cycles of hipA induction, growth arrest and regrowth phases. In the multiple conditions tested, we observed that the length of growth arrest became successively shorter for each round of induction. We verified that this was not due to the appearance of HipA-resistant mutants. Additionally, we identified conditions, such as the growth phase of the starting culture and growth vessels, that alter the length of growth arrest. Our results showed that the length of HipA-induced growth arrest was dependent on environmental factors-in particular, the past growth environment of cells, such as a previous hipA induction. These effects lasted even after multiple rounds of cell divisions, indicating the presence of cellular "memory" that impacts cells' response to HipA-induced toxicity.

Isolation and genomic analysis of 11-aminoundecanoic acid-degrading bacterium Pseudomonas sp. JG-B from nylon 11 enrichment culture.

Nylon 11 is a polymer synthesized from 11-aminoundecanoic acid, and widely used in commercial manufacturing. In this study, we describe the isolation of the first organism capable of metabolizing 11-aminoundecanoic acid from nylon 11 enrichment culture. The strain shows rapid growth on 11-aminoundecanoic acid as a sole source of carbon, nitrogen, and energy. Furthermore, the genome sequence of strain JG-B was deciphered and shown to belong to genus Pseudomonas. Many genes encoding putative extracellular hydrolases, as well as homologues of nylon 6 hydrolases (NylB and NylA) were identified, suggesting the metabolic versatility and possibility that this organism could also depolymerase nylon 11 polymers.

Comparative Proteomic Analysis of Propane Metabolism in Mycobacterium sp. Strain ENV421 and Rhodococcus sp. Strain ENV425.

While growing on propane as a sole source of carbon, many strains cometabolically degrade environmental pollutants, such as ethers and chlorinated hydrocarbons. To gain insights into the molecular basis behind such a high metabolic versatility of propanotrophs, we examined the propane-inducible protein expression patterns of 2 soil actinobacteria that are known to degrade a variety of ethers (i.e., Mycobacterium sp. strain ENV421 and Rhodococcus sp. strain ENV425). In both strains, soluble diiron monooxygenase(s), that would catalyze the first step of the pathway, were induced by propane. However, despite their phylogenetic similarity, different sets of additional putative propane oxygenases (e.g., cytochrome P450 and particulate methane monooxygenases) were overexpressed in the 2 strains. They also diverged in the expression of enzymes responsible for downstream reactions. This study revealed a diversity of expression of putative propane oxygenases, which may be responsible for xenobiotic degradation, as well as a variety of metabolic pathways for propane in these bacterial species.

Genomic Analysis of Propane Metabolism in Methyl Tert-Butyl Ether-Degrading Mycobacterium Sp. Strain ENV421.

Methyl tert-butyl ether (MTBE) is a ground water contaminant with plausible carcinogenic properties. Mycobacterium sp. strain ENV421 cometabolically degrades MTBE and other ethers during the growth on propane as a carbon source. In this study, the 6.2 Mb genome of strain ENV421 was deciphered. The genome sequence revealed the presence of numerous putative propane catabolic genes including genes encoding hydrocarbon oxygenases and short chain alcohol dehydrogenases. These data provide the basis for the elucidation of propane metabolic pathways in strain ENV421 and its application for the remediation of ground water contaminated with toxic ethers.

Draft Genome Sequence of a Propanotroph, Rhodococcus sp. Strain ENV425, Capable of Degrading Methyl tert-Butyl Ether and N-Nitrosodimethylamine.

In this study, the draft genome of Rhodococcus sp. strain ENV425 was determined. The propane-grown strain ENV425 cometabolically degrades environmental contaminants such as methyl tert-butyl ether and N-nitrosodimethylamine. The sequence revealed the presence of multiple hydrocarbon metabolic genes that could play pivotal roles in the biodegradation of pollutants.