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Microalgae have received continued attention as a potential source for biofuel production. However, the lack of suitable strains that provide a lipid-rich biomass and tolerate harsh condition inhibits their industrial application. This report describes an effort to transform Synechocystis sp. with genes encoding acetyl-CoA carboxylase (ACC), a key regulatory enzyme in the lipogenesis pathway, from the white mustard plant (Sinapis alba) and the bacterium Escherichia coli DH5α using chitosan nanoparticles. Although a recombinant plasmid encoding S. alba ACC failed to express, successful transformation was achieved with a recombinant plasmid encoding E. coli DH5α ACC. The successful transformant, Synechocystis sp. PAK13, exhibited increased ACC expression compared with its wild-type parent (11.8 vs. 7.2 ng), which significantly increased its lipid content (by 3.6-fold). Synechocystis sp. PAK13 also exhibited a significant (20%) reduction in photosynthetic pigments, a 1.52-fold higher glucose content and a 3.5-fold lower sucrose content than the wild-type. In conclusion, this report introduces a useful strategy to overexpress the ACC gene in microalgae, creating strains with improved lipid production that are suited to industrial applications.

From the active acetone fraction of Chenopodium murale, vanillic acid was isolated and identified, based on 1H and 13C nuclear magnetic resonance spectral analyses. Free phenolic compounds inside the active acetone were qualified and quantified by using high performance liquid chromatography analysis, which revealed the presence of seven compounds with an abundance of vanillic and p-hydroxybenzoic acids. The allelopathic potential of the acetone fraction and vanillic acid was evaluated through laboratory bioassays against tomato plants. Our results showed that the allelopathic potential induced by low concentrations of the acetone fraction and vanillic acid stimulated the germination and growth of tomato and had stimulating effects on the activity of some antioxidant enzymes. We observed an enhancement in the activity of catalase, peroxidase, superoxide dismutase, and polyphenol oxidase, as well as the content of soluble protein and phenolic glycoside. Meanwhile, the levels of free phenolic compounds, H2O2, and lipid peroxidation decreased. The highest stimulations were recorded at 50 p.p.m. of acetone fraction and 0.5 p.p.m. of vanillic acid. In contrast, the highest concentrations exerted negative effects on all the measured parameters to record the maximum value of inhibition at 400 p.p.m. of acetone fraction and 4 p.p.m. of vanillic acid. These results proved the antioxidative effects of active acetone and vanillic acid at low concentrations and their potent use as a stimulator for tomato germination and growth.

Synechococcus has the ability to grow at temperatures lower than their normal growth temperature, although at a relatively reduced rate. Gel electrophoretic analysis of cellular proteins from cold — treated and heat shocked cells labeled with 14 C-protein hydrolysate revealed differences in the pattern of protein synthesis. The molecular weights of polypeptides induced at low temperatures (10 – 22 °C) were estimated to be 74, 64.5, 23, 17 and 14.7 kDa. Time course studies indicated progressive induction of some cold shock proteins (CSPs) at 13 °C. Heat shock (HS) involved immediate repression of most non heat shock proteins and identification of newly synthesized protein bands with molecular weights estimated to fall into the range characteristic for HS. The results revealed that in Synechococcus the photosynthetic activity and the midpoint value for critical temperature regions are dependent on growth temperature. The reduction in O 2 — evolution ranged between 37% to 47% within the studied low temperature range. Treatment at 10 and 13 °C showed rapid loss of activity (50%) after 17 and 29 min, respectively. Furthermore, treatment at 13 °C produced a change in light absorption spectrum A pattern which indicated the involvement of a common mechanism in the cold susceptibility of photosynthesis and absorption spectrum. It is suggested that cold induced particle movement which lead to functional detachment of phycobilisomes away from the Chl-protein complex or vice versa.

Lemna gibba grown on mixtures of Nile-to-wastewater ratio of 1:1 (C) and 1:3 (D) exhibited maximum gain in fresh and dry weights. The Lemna system was capable of efficient quantitative and qualitative algal reduction. Maximum efficiency in algal removal was achieved in mixture “C” (94.4%). The ammonia rate of reduction was markedly high in mixtures enriched with wastewater with a complete depletion of any detectable nitrogen. The protein content in Lemna tissue increased upon enrichment with wastewater, and reached a maximum of 47.1% in mixture “D,” with a maximum increase in all amino acids. Lys content markedly increased by 105%. The treatment showed a maximum reduction in Fe and Zn in water mixture “D,” which correlated with their maximum bioaccumulation level in L. gibba tissue. Lemna gibba performed 100% efficient Mn removal after 16 days in all treated mixtures with minimum accumulation in the tissue.

The response to the extract of the Egyptian wild herb Calendula micrantha, with molluscicidal activity, was examined in the unicellular cyanobacterium Synechococcus sp. strain PCC 6301. Growth and chlorophyll a of the cells were only slightly affected by low concentrations but drastically reduced by high concentrations. The rate of protein synthesis progressively decreased by increasing extract concentration. The cells preferentially induced the synthesis of a limited number of polypeptides in response to the treatment. Among the induced polypeptides were those with apparent molecular weights of 161K (161,000), 96.7K, 93.4K, 85K, 69.9K, 59K, 49K, 45K, 35K, 32.4K, 28K, 24K, 21.7K, 18K, and 16K based on their mobilities in gel electrophoresis. These initial studies suggest that the plant extract exerted certain stress which stimulated alteration in the pattern of protein synthesis in Synechococcus sp. Some of the induced polypeptides are similar to that known to occur in other stresses, especially heat-shock stress.

The cyanobacteriumSynechocystis PCC 6803 was grown photoautotrophically in an inorganic medium at constant growth temperatures of 20, 38 (control) or 43°C for 9 h. The up and down-shift of cultivation temperature decreased the growth as measured by culture absorbance and chlorophylla content. However, high temperature slightly increased the oxygen evolution while temperature lower than control inhibited oxygen evolution during the whole incubation period. The protein synthesis studied by14C-labeled protein declined under low temperature by about 50%. The fatty acid pattern is characterized as lacking in C20/C22 acids but containing large amounts of C16 and C18 polyunsaturated fatty acids, 16:2 and 18:3 in particular. The lower temperature increased the percentage of monounsaturated fatty acids while higher temperature increased the saturated fatty acid content in total lipids and lipid classes studied.

Sublethal atrazine concentrations induced a general inhibition on growth, photosynthesis, and dark respiration in the green alga Chlorella kessleri. 14C-protein hydrolysate indicated a maximum incorporation level by 5 microM atrazine after 48 hr. Progressive reduction in protein synthesis was associated with increasing herbicide concentration at all experimental periods. The herbicide had preferential effect on the associated fatty acid composition of total and phospholipids. After 24 and 48 hr the herbicide stimulated fatty acids synthesis at concentrations where photosynthesis was inhibited. Meanwhile, stearic and miristic acids disappeared at 15 microM after 24 hr and the total polyunsaturated fatty acids were not affected after 48 hr. Fatty acid synthesis was sensitive to treatment at 72 hr by 5 and 10 microM atrazine, whereas the total saturated fatty acids were completely inhibited.

The isolation and characterization of cyanogen bromide peptides derived from the human gingival collagen of patients with chronic periodontitis revealed the presence of both Type I and Type III collagens in this tissue. The amount of Type III collagen, however, was found to be lower than that in normal gingival tissue. In addition, a non-collagenous protein fraction, accounting for approximately 20% of the insoluble matrix, was relatively rich in acidic, hydrophobic, and hydroxy-containing amino acids. Amino acid analysis, likewise, revealed qualitative and quantitative differences between the normal and diseased tissues.