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The bacteria wall fulfills important physiological functions at the cell, depending on its composition and organization. Many researches focused their studies in understanding the change of its properties not only in strength and permeability, but also in morphological plasticity due to both chemical and physical stresses. In particular, filamentation morphology is a cryptic phenomenon, with involve for great variety of bacteria, which allow them to acquire adaptive benefits. This phenotypic alteration consists of an alteration or lack of cell septation during the cell growth, as consequence of DNA damage or development of stress, such as nutritional factors, antibiotic resistance, low temperature, non-availability of oxygen, high osmolarity, and antimicrobial agents. These cells result in modification of elongation 10–50 times, thickness, chemical composition, and extent of cross-linking of the cell wall polymers than normal-shaped cells. Moreover, the advancement in the morphology engineering permitted the manipulation of the genes encoding the proteins belonging to the plasma membrane or cytoplasm, to have the control over the bacterial shapes and of the its cytoplasmatic environment. In biotechnology application, the intracellular space is primary used for a greater accumulation of secondary products, such as polyhydroxyalkanoates (PHAs). This review provides an insight into environmental induction of filamentation morphology and its use in biotechnological process. Key points: • Environmental stresses inducing filamentation morphology • Morphology engineering in biotechnological processes • Increase of polyhydroxyalkanoates (PHAs) accumulation. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are considerable biopolymers that have gained an increasing biotechnological interest in different applications, although their industrial production presents several limitations. Filamentous bacterial cells could represent a possible strategy to increase PHA yield, since more abundant PHA inclusions can be stored in elongated than in rod-shaped cells. At first, we determined the optimal batch culture conditions to induce filamentation in Pseudomonas mediterranea CFBP-5447T, using glutamine, glycerol, glucose, and sodium octanoate, as the sole carbon source, at low- (100 rpm) or high- (250 rpm) shaking speeds. Successively, a fermentative process was set up using glutamine in a co-metabolic strategy with glycerol, and the PHAs production was compared in rod-shaped and filamentous cells. High glutamine concentrations (from 28 to 56 mM) were able to induce alone filamentation, whereas at lower glutamine concentrations (5–10 mM), the shaking speeds became critical to allow or not filamentous phenotype. PHA granule production was higher in filamentous than in rod-shaped cells, when glycerol (46.6 mM) was added to glutamine (5 mM) in co-metabolism, and fermentation was performed at a low-shaking speed. After extraction and precipitation, PHA yield was about two times higher in filamentous than that rod-shaped cells. Our results provide new insights into filament-inducing conditions and indicate a potential use of filamentous P. mediterranea CFBP-5447T cells to increase PHA yield. These findings could have great advantages in PHAs recovering during downstream processes, since the harvesting of elongated cells is much less time-consuming and energy expensive than required with rod-shaped cells. [ABSTRACT FROM AUTHOR]