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Proteome profile changes during poly-hydroxybutyrate intracellular mobilization in gram positive Bacillus cereus tsu1.

ABSTRACT: BACKGROUND:Bacillus cereus is a bacterial species which grows efficiently on a wide range of carbon sources and accumulates biopolymer poly-hydroxybutyrate (PHB) up to 80% cell dry weight. PHB is an aliphatic polymer produced and stored intracellularly as a reservoir of carbon and energy, its mobilization is a key biological process for sporulation in Bacillus spp. Previously, B. cereus tsu1 was isolated and cultured on rapeseed cake substrate (RCS), with maximum of PHB accumulation reached within 12?h, and depleted after 48?h. Fore-spore and spore structure were observed after 24?h culture. RESULTS:Quantitative proteomic analysis of B. cereus tsu1 identified 2952 quantifiable proteins, and 244 significantly changed proteins (SCPs) in the 24?h:12?h pair of samples, and 325 SCPs in the 48?h:12?h pair of samples. Based on gene ontology classification analysis, biological processes enriched only in the 24?h:12?h SCPs include purine nucleotide metabolism, protein folding, metal ion homeostasis, response to stress, carboxylic acid catabolism, and cellular amino acid catabolism. The 48?h:12?h SCPs were enriched into processes including carbohydrate metabolism, protein metabolism, oxidative phosphorylation, and formation of translation ternary structure. A key enzyme for PHB metabolism, poly(R)-hydroxyalkanoic acid synthase (PhaC, KGT44865) accumulated significantly higher in 12?h-culture. Sporulation related proteins SigF and SpoEII were significantly higher in 24?h-samples. Enzymes for nitrate respiration and fermentation accumulated to the highest abundance level in 48?h-culture. CONCLUSIONS:Changes in proteome of B. cereus tsu1 during PHB intracellular mobilization were characterized in this study. The key enzyme PhaC for PHB synthesis increased significantly after 12?h-culture which supports the highest PHB accumulation at this time point. The protein abundance level of SpoIIE and SigF also increased, correlating with sporulation in 24?h-culture. Enzymes for nitrate respiration and fermentation were significantly induced in 48?h-culture which indicates the depletion of oxygen at this stage and carbon flow towards fermentative growth. Results from this study provide insights into proteome profile changes during PHB accumulation and reuse, which can be applied to achieve a higher PHB yield and to improve bacterial growth performance and stress resistance.

SUBMITTER: Li H

PROVIDER: S-EPMC7236355 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Proteome profile changes during poly-hydroxybutyrate intracellular mobilization in gram positive Bacillus cereus tsu1.

Li Hui H O'Hair Joshua J Thapa Santosh S Bhatti Sarabjit S Zhou Suping S Yang Yong Y Fish Tara T Thannhauser Theodore W TW

BMC microbiology 20200519 1

<h4>Background</h4>Bacillus cereus is a bacterial species which grows efficiently on a wide range of carbon sources and accumulates biopolymer poly-hydroxybutyrate (PHB) up to 80% cell dry weight. PHB is an aliphatic polymer produced and stored intracellularly as a reservoir of carbon and energy, its mobilization is a key biological process for sporulation in Bacillus spp. Previously, B. cereus tsu1 was isolated and cultured on rapeseed cake substrate (RCS), with maximum of PHB accumulation reac ...[more]

PMID: 32429845

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Project description:Under conditions of carbon starvation or thermal, osmotic, or oxidative shock, mutants affected in the synthesis or mobilization of poly-3-hydroxybutyrate (PHB) are known to survive less well. It is still unclear if the synthesis and accumulation of PHB are sufficient to protect bacteria against stress conditions or if the stored PHB has to be mobilized. Here, we demonstrated that mobilization of PHB in Herbaspirillum seropedicae SmR1 was heat-shock activated at 45°C. In situ proton (1H) nuclear magnetic resonance spectroscopy (i.e., 1H-nuclear magnetic resonance) showed that heat shock increased amounts of 3-hydroxybutyrate (3HB) only in H. seropedicae strains able to synthesize and mobilize PHB. H. seropedicae SmR1 mutants unable to synthesize or mobilize PHB were more susceptible to heat shock and survived less well than the parental strain. When 100 mM 3-hydroxybutyrate was added to the medium, the ΔphaC1 strain (an H. seropedicae mutant unable to synthesize PHB) and the double mutant with deletion of both phaZ1 and phaZ2 (i.e., ΔphaZ1.2) (unable to mobilize PHB) showed partial rescue of heat adaptability (from 0% survival without 3HB to 40% of the initial viable population). Addition of 200 mM 3HB before the imposition of heat shock reduced protein aggregation to 15% in the ΔphaC1 mutant and 12% in the ΔphaZ1.2 mutant. We conclude that H. seropedicae SmR1 is naturally protected by 3HB released by PHB mobilization, while mutants unable to generate large amounts of 3HB under heat shock conditions are less able to cope with heat damage.IMPORTANCE Bacteria are subject to abrupt changes in environmental conditions affecting their growth, requiring rapid adaptation. Increasing the concentration of some metabolites can protect bacteria from hostile conditions that lead to protein denaturation and precipitation, as well as damage to plasma membranes. In this work, we demonstrated that under thermal shock, the bacterium Herbaspirillum seropedicae depolymerized its intracellular stock polymer known as poly-3-hydroxybutyrate (PHB), rapidly increasing the concentration of 3-hydroxybutyrate (3HB) and decreasing protein precipitation by thermal denaturation. Mutant H. seropedicae strains unable to produce or depolymerize PHB suffered irreparable damage during thermal shock, resulting in fast death when incubated at 45°C. Our results will contribute to the development of bacteria better adapted to high temperatures found either in natural conditions or in industrial processes. In the case of H. seropedicae and other bacteria that interact beneficially with plants, the understanding of PHB metabolism can be decisive for the development of more-competitive strains and their application as biofertilizers in agriculture.

Dataset Information

Proteome profile changes during poly-hydroxybutyrate intracellular mobilization in gram positive Bacillus cereus tsu1.

Publications

Proteome profile changes during poly-hydroxybutyrate intracellular mobilization in gram positive Bacillus cereus tsu1.

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