Metabolic engineering of Synechococcus elongatus for photoautotrophic production of mannitol

With multiple applications in food, pharmaceutical, and chemical industries as antioxidant or nonmetabolizable sweetener; the bioproduction of d -mannitol is gaining global attention, especially with photosynthetic organisms as hosts. Considering the sustainability prospects, the current work encompasses metabolic engineering of a widely used cyanobacterial strain, Synechococcus elongatus PCC 7942, and two newly isolated fast-growing cyanobacterial strains; S. elongatus PCC 11801 and S. elongatus PCC 11802, for mannitol production. We engineered these strains with a two-step pathway by cloning genes for mannitol-1-phosphate dehydrogenase (mtlD) and mannitol-1-phosphatase (mlp), where the mtlD expression was under the control of different promoters from PCC 7942, namely, P_rbc225, P_cpcB300, P_cpcBm1, P_rbcLm17, and P_rbcLm15. The strains were tested under the “switch conditions,” where the growth conditions were switched after the first 3 days, thereby resulting in differential promoter activity. Among the engineered strains of PCC 11801 and PCC 11802, the strains possessing P_rbc225-mtlD module produced relatively high mannitol titers of 401 ± 18 mg/L and 537 ± 18 mg/L, respectively. The highest mannitol titer of 701 ± 15 mg/L (productivity 60 mg/L.d, yield 895 µM/OD₇₃₀) was exhibited by the engineered strain of PCC 7942 expressing P_cpcB300-mtlD module. It is by far the highest obtained mannitol yield from the engineered cyanobacteria.     

MORPHOLOGY AND GENETICS OF A PERIODIC COLONIAL MUTANT OF NEUROSPORA CRASSA

A mutant of strain 69–1113a of Neurospora crassa, which shows periodic growth upon both complete and minimal media, was named “clock,” and some of the morphological and genetic differences between this mutant and the “patch” and “wild” strains were investigated. In contrast to the uniform growth of “wild,” the “clock” mutant produces a series of bands formed by cymelike aggregations of hyphae which become progressively more dense and finally mark the end (front) of a growth band. A new growth band is formed by a number of hyphae which grow out as in “wild” strains and dichotomize and form new cymes which again become progressively more dense and finally form a new front. It is shown that “clock” continues its rhythmic growth when cultured in continuous darkness. Some “wild” strains were induced to grow periodically on appropriate media. A medium containing equal quantities of sorbose and sucrose caused strain 65–811A (a “wild”) to produce the “patch” type growth. Random isolation, as well as ordered isolation, of ascospores following a cross between “wild” and “clock” show a 1: 1 segregation indicating that “clock” differs from “wild” by a single gene.     

HETEROGENEITY OF THE CYANOBACTERIAL GENUS SYNECHOCYSTIS AND DESCRIPTION OF A NEW GENUS,GEMINOCYSTIS1

The study and revision of the unicellular cyanobacterial genus Synechocystis was based on the type species S. aquatilis Sauv. and strain PCC 6803, a reference strain for this species. Uniformity in rRNA gene sequence, morphology, and ultrastructure was observed in all available Synechocystis strains, with the exception of the strain PCC 6308, which has been considered by some to be a model strain for Synechocystis. This strain differs substantially from the typical Synechocystis cluster according to both molecular (<90% of similarity, differences in 16S–23S rRNA internal transcribed spacer [ITS] secondary structure) and phenotypic criteria (different ultrastructure of cells). This strain is herein classified into the new genus Geminocystis gen. nov., as a sister taxon to the genus Cyanobacterium. Geminocystis differs from Cyanobacterium by genetic position (<94.4% of similarity) and more importantly by its different type of cell division. Because strain PCC 6308 was designated as a reference strain of the Synechocystis cluster 1 in Bergey’s Manual, the members of this genetic cluster have to be revised and reclassified into Geminocystis gen. nov. Only the members of the Synechocystis cluster 2 allied with PCC 6803 correspond both genetically and phenotypically to the type species of the genus Synechocystis (S. aquatilis).     

Relationship among acidophilic bacteria from diverse environments as determined by randomly amplified polymorphic DNA analysis (RAPD)

Summary Random amplification of polymorphic DNA (RAPD), a PCR-based technique was applied to evaluate genomic diversity among three strains of Acidithiobacillus thiooxidans, five strains of Acidithiobacillus ferrooxidans and one acidophilic moderate thermophile strain, using 45 random primers of five different series. More than 2200 bands were observed, with an average of 45 bands per primer. Primer OPC-3 produced the maximum number of fragments whereas minimum numbers of fragments were produced with primer OPA-5. A dendrogram was generated using cluster analysis by the unweighted pair group method of arithmetic means (UPGMA). The dendrogram showed three groups with similarity ranging from 29 to 85%. The maximum similarity (85%) was observed between the strains T.t₁ and T.t₂ of Acidithiobacillus thiooxidans.     

Further Electrophoretic Characterization of Strains of Tetrahymena pyriformis*

Mobility patterns of 5 isozymes in strains of Tetrahymena pyriformis were demonstrated using polyacrylamide disc gel electrophoresis. Six stock strains were compared in these patterns to 4 strains representative of each of the previously described 4 major “phenotypic sets.” Stock strains segregated into predicted “phenosets,” and essentially confirmed validity and reproducibility of such a discrimination method. The proposal that new strain designations be assigned on a basis of “phenoset” conformity is reaffirmed.     

GENETIC, MORPHOLOGICAL, AND TOXICOLOGICAL VARIATION AMONG GLOBALLY DISTRIBUTED STRAINS OF NODULARIA (CYANOBACTERIA)

Morphological, toxicological, and genetic variation was examined among 19 strains of Nodularia. The strains examined could be morphologically discriminated into four groups corresponding to N. spumigena Mertens, N. sphaerocarpa Bornet et Flahault, and two strains that did not clearly correspond to currently accepted Nodularia species. Genetic variation was examined using nucleotide sequencing of the phycocyanin intergenic spacer region (cpcBA-IGS) and RAPD-PCR. The PCR-RFLP of the cpcBA-IGS differentiated four genotypes corresponding to the four morphological groups. However, nucleotide sequencing of 598 bp of the 690-bp fragment showed that one of the three strains corresponding to N. sphaerocarpa (PCC 7804) was genetically divergent from the other two, suggesting that it constitutes a distinct species. Nucleotide variation within the morphospecies groups was limited (<1%), and all 14 Australian strains of N. spumigena possessed identical cpcBA-IGS sequences. The RAPD-PCR differentiated the same groups as the cpcBA sequencing and discriminated each of the seven different Australian populations of N. spumigena. Strains from within a bloom appeared genetically identical; however, strains isolated from different blooms could be separated into either a western or a southeastern Australian cluster, with one strain from western Australia showing considerable genetic divergence. The pattern of variation suggests that individual blooms of N. spumigena are clonal but also that Australian N. spumigena populations are genetically distinct from each other. Examination of genetic distance within and between blooms and within and between morphological groups showed clear genetic dicontinuities that, in combination with the cpcBA-IGS data, suggest that Nodularia contains genetically distinct morphospecies rather than a continuous cline of genetic variation. Furthermore, these morphospecies are genetically variable, exhibiting hierarchical patterns of genetic variation on regional and global scales. Production of the hepatotoxin nodularin was not restricted to one genetic lineage but was distributed across three of the five genotypic groups. A strain of N. spumigena from a nontoxic Australian population was found to fall within the range of genetic variation for other toxic Australian strains and appears to be a unique nontoxic strain that might have arisen by loss of toxin production capacity.     

GENETIC VARIANCE FOR RATE OF POPULATION INCREASE IN NATURAL POPULATIONS OF FLOUR BEETLES,TRIBOLIUM SPP.

The genetic and ecological effects of population subdividsion were investigated for two wild strains of Tribolium castaneum and two wild strains of T. confusum and compared with the effects of population subdivision on the synthetic laboratory strain of T. castaneum (c-SM), used extensively in earlier experiments. For the c-SM strain, it has been shown repeatedly, for a variety of different population structures (different combinations of effective numbers, N_e, and migration rates, m), that large heritable differences in population growth rate arise among demes during 10 to 15 generations of population subdivision. Because this laboratory strain was synthesized by mass mating several “inbred” strains in 1973 (80 to 100 generations ago), it is possible that it has genetic variation for fitness (measured as the heritable variance among demes in the rate of population increase) unusually large compared to natural populations of flour beetles. In this paper, I report that natural populations of flour beetle exhibit as much or more phenotypic and genetic variation in the effects of population structure on fitness than the laboratory strain, c-SM. The observation of substantial heritable variation for fitness in natural populations is unexpected under additive theory and may be indicative of nonadditive genetic variance.     

Vergleich eines "glatten" und eines "rauhen" Stammes von Pseudomonas syringae pv. phaseolicola

Comparison of a “smooth” and a “rough” isolate of Pseudomonas syringae pv. phaseolicola The “smooth” (S) wild strain of Pseudomonas syringae pv. phaseolicola was compared with a “rough” (R) variant of low virulence. Both strains grew nearly equally well on a sucrose containing medium with yeast extract and casamino acids, and the strains did not differ markedly in the quantity of produced EPS (= extracellular polysaccharides). Principally the same results were obtained for high and medium concentrations of sucrose, or when sucrose was replaced by glucose or fructose. However, on glucose and fructose considerably lower quantities of EPS were produced. The biological activity of S-EPS was higher than that of R-EPS. This difference between the EPS preparations was not as marked as leaf inoculation with both bacterial isolates. After prolonged bacterial culture the EPS-production increased further, so that the differences between both strains decreased. A different EPS type was produced on the glycerol containing medium of KING B. Variations in the composition of this medium resulted in different morphology of the agar grown cultures, and the relative differences between S and R bacteria changed. When 62 different physiological tests for both bacterial strains were compared, the “rough” bacteria revealed a lowered range of positive reactions, with a few exceptions. However, it appeared unlikely that the reduced virulence of the “rough” bacteria was due to these differences. Obviously, defects in the extracellular products, but not in levan, were responsible for the reduction of virulence.     

PHYLOGENETIC PATTERNS AMONG NOSTOC CYANOBIONTS WITHIN BI‐ AND TRIPARTITE LICHENS OF THE GENUS PANNARIA1

Phylogenetic relationships between Nostoc cyanobionts in the lichen genus Pannaria were studied to evaluate their correlation to geography, habitat ecology, and other patterns previously reported. The 16S rRNA gene sequences of a total of 37 samples of 21 Pannaria species from seven countries from the Northern and Southern hemispheres were analyzed and compared with 69 free‐living and symbiotic cyanobacterial strains. The sequences from Pannaria were distributed throughout a branch of Nostoc sequences previously called “the Nephroma guild,” and within two subgroups from another branch, referred to as the “Peltigera guild,” although there was a gradual transition between the two major groups. There is a more diverse pattern of relationships between Nostoc sequences from bipartite versus tripartite lichen species in Pannaria, compared with other well‐studied genera, such as Nephroma and Peltigera. Cyanobionts from several tripartite Pannaria species from the Southern Hemisphere and corticolous bipartite species from both hemispheres were grouped together. Four sequences of Pannaria and Pseudocyphellaria cyanobionts from rocks in the Chilean Juan Fernández Islands were nested within corticolous cyanobionts, whereas the terricolous “Pannaria sphinctrina clade” was placed with other terricolous strains. The cluster patterns derived from phylogenetic analysis were partly reflecting lichen taxonomy, in two groups of lichen species, possibly indicating coevolution. The phylogram partly also reflected lichen ecology. Three Pannaria species have very different cyanobiont strains when they grow in different habitats.     

Characterization of Growth and Metabolism of Commercial Strains of Propionic Acid Bacteria by Pressure Measurement

Dairy propionibacteria are essential starters for Emmental cheese manufacture. The behavior of three commercial strains of Propionibacterium freudenreichii subsp. shermanii (P.f. 1, P.f. 2 and P.f 3) were studied in a liquid medium under air and N₂ atmosphere using an on‐line pressure measurement technique. Growth kinetics and metabolite production were characterized under conditions usually reported as “optimal conditions” (pH 6.5, NaCl 0 %, temperature 30 °C) and also evaluated under “stressful conditions” (pH 5.2, NaCl 2 %, temperature 20 °C) simulating the cheese ripening conditions. In both cases, the effects of oxygen on growth were strain‐dependent. Under “stressful conditions”, two of the three strains were inhibited by oxygen under conditions of air atmosphere, while all three strains grew under conditions of N₂ atmosphere. In the latter case, the duration of the lag phase and the maximum rate of pressure variation were significantly different, however, no significant differences were found between the strains with regard to the total fermentation time. Under “optimal conditions” metabolite production was strain‐dependent. In an air atmosphere, all strains produced more acetate and CO₂ and less propionate than in a nitrogen atmosphere.     

Association of two groups of phytoplasma with various symptoms in some wooden and herbaceous plants

During 2015–2016, wooden and herbaceous plants growing in parks, boulevards, fields, gardens and forests in Khuzestan province, southwestern Iran, were visually inspected for symptoms resembling phytoplasma. Fifty‐one symptomatic samples from nine different species and one symptomless sample from each plant were collected. Leaf midribs, petioles and the parts of stem cambium were separated and freeze‐dried. Total DNA was extracted using CTAB‐based method and tested for phytoplasma using a nested PCR assay. The expected size amplicons of 16S rDNA were sequenced and compared to those of reference phytoplasmas by BLASTn search and phylogenetic analysis. The consensus 16S rDNA sequence of the detected phytoplasma in narrow cattail related to reference phytoplasma group 16SrVI, “Candidatus Phytoplasma trifolii” while in the other plants were related to reference phytoplasma subgroup 16SrII–D, “Candidatus Phytoplasma aurantifolia.” All isolates showed 98%–99% sequence identity to members of their reference groups. To our knowledge, this is the first report of “Candidatus Phytoplasma aurantifolia”‐related strains infecting the plants of Acacia salicina, Alternanthera ficoidea, Melaleuca citrine, Citrus aurantium throughout the world and Celosia christata in Iran. Furthermore, this study is the first to report the association of a “Candidatus Phytoplasma trifolii”‐related strain with Typha angustifolia worldwide.     

Taxonomic Attribution of “<Emphasis Type="Italic">Oscillatoriales</Emphasis>” Strains within the Bacteriological System of Cyanobacteria: Identification Algorithm for Operational Genera

In “Oscillatoriales” cyanobacteria (Cyanophyceae), relatively simple and uniform morphology superimposes on high genetic diversity that impedes reliable identification. The system of Cyanobacteria set forth in Bergey’s Manual of Systematic Bacteriology-2001/Systematics of Archaea and Bacteria-2015 deals with operational taxa—form-genera (“larger” genera represented by strains) unlike true cyanophycean genera represented by species. Form-genera were established on morphological criteria shared with Cyanophyceae, although they were typified by Pasteur Culture Collection (PCC) strains. Despite being important in determinative cyanobacteriology, old diagnoses of form-genera should be reappraised because, in them: (i) vague and/or ephemeral morphological characters are considered taxonomically significant; (ii) phylogenetic character, such as 16S rRNA gene sequence (16S) is missing. We identified 32 “Oscillatoriales” strains from CALU collection (St. Petersburg University, Russia) basing on core morphology traits, 16S of PCC type strains, and 16S from GenBank database. We proposed that, in experimentally oriented and ecology oriented studies, unequivocal identification can be attained via triple match: streamlined form-genus diagnosis— 16S of PCC reference strain—GenBank most similar 16S. Additionally, we traced the phylogeny of “Oscillatoriales” form-genera via 16S clustering and HIP1 fingerprinting, and suggested that these operational taxa should be replaced with monophyletic assemblages. Nucleotide sequence data reported are available in the GenBank database under the accession numbers KX263921?KX263950.     

Occurrence of a novel strain of Scirtothrips dorsalis (Thysanoptera: Thripidae) in Japan and development of its molecular diagnostics

Scirtothrips dorsalis Hood is a cosmopolitan and polyphagous thrips species. Recently, a novel strain of S. dorsalis attacking capsicum crops was found in Japan. A molecular phylogenetic analysis using mitochondrial cytochrome c oxidase subunit I sequences revealed that the capsicum-associated populations were genetically different from Japanese native strains and were closely related to Southeast Asian populations. We named the capsicum-associated populations “strain C” and the Japanese native ones “strain YT”. A total of 10 haplotypes were found in strain C and 26 in strain YT. To differentiate the two strains, we developed a multiplex-PCR method using the ribosomal ITS2 region.     

STUDIES ON THE KINETICS OF ACETYLCHOLINESTERASE IN THE RESISIANT AND SUSCEPTIBLE STRAINS OF HOUSEFLY (MUSCA DOMESTICA)

Abstract Acetylcholinesterase (AChE) in the susceptible (S) and the resistant (R) strains of housefly (Musca domestica) was investigated using kinetic analysis. The V_max values of AChE for hydrolyzing acetylthiocholine (ATCh) and butyrylthiocholine (BTCh) were 4578.50 and 1716.08nmol/min/mg* protein in the R strain, and were 1884.75 and 864.72 nmol/min/mg. protein in the Sstrain, respectively. The V_max ratios of R to S enzyme were 2.43 for ATCh and 1.98 for BTCh. The K_m values of AChE for ATCh and BTCh were 0.069 and 0.034 mmol/L in the S strain, and 0.156, 0.059 mmol/L in the R strain, respectively. The K_m ratios of R to S enzyme were 2.26 for ATCh and 1.74 for BTCh. The k_i ratios of S to R enzyme for three insecticides propoxur, methomyl and paraoxon were 46.04, 4.17 and 2. 86, respectively. In addition, k_cat and k_cat/K_m for measuring turnover and catalytic efficiency of AChE were determined using eserine as titrant. The k_cat values of AChE from the R strain for both ATCh and BTCh were higher than those values from the S strain. But the values of k_cat/K_m were in contrary to the k_cat values with R enzyme compared to S enzyme. The AChE catalytic properties and sensitivity to the inhibition by three insecticides in the R and S strains of housefly were discussed based on contribution of V_max, K_m, k_i, k_cat and k_cat/K_m. All these data implied that AChE from the R strain might be qualitatively altered. We also observed an intriguing phenomenon that inhibitors could enhance the activity of AChE from the resistant strain. This “flight reaction” of the powerful enzyme might be correlated with the developing resistance of housefly to organophosphate or carbamate insecticides.     

Metabolic engineering of Synechocystis sp. PCC 6803 for enhanced ethanol production based on flux balance analysis

Synechocystis sp. PCC 6803 is an attractive host for bio-ethanol production due to its ability to directly convert atmospheric carbon dioxide into ethanol using photosystems. To enhance ethanol production in Synechocystis sp. PCC 6803, metabolic engineering was performed based on in silico simulations, using the genome-scale metabolic model. Comprehensive reaction knockout simulations by flux balance analysis predicted that the knockout of NAD(P)H dehydrogenase enhanced ethanol production under photoautotrophic conditions, where ammonium is the nitrogen source. This deletion inhibits the re-oxidation of NAD(P)H, which is generated by ferredoxin-NADP⁺ reductase and imposes re-oxidation in the ethanol synthesis pathway. The effect of deleting the ndhF1 gene, which encodes NADH dehydrogenase subunit 5, on ethanol production was experimentally evaluated using ethanol-producing strains of Synechocystis sp. PCC 6803. The ethanol titer of the ethanol-producing ∆ndhF1 strain increased by 145%, compared with that of the control strain.

     

Intrachain reactions of a pair of reactive groups attached to polymer ends. V. Formation of disulfide linkages in the air-oxidation of sulfhydryl groups attached to ends of polysarcosine chain

Polysarcosine having sulfhydryl groups attached to both ends was synthesized by the NCA method and its air-oxidation was investigated in aqueous solution with cupric-ion or ferric-ion catalysts. Air-oxidation was also conducted for a polysarcosine having one terminal sulfhydryl group. The product of the air-oxidation was fractionated by gel chromatography. The product analysis of the fully oxidized monofunctional polymer showed that the sulfhydryl groups were converted into disulfide bonds exclusively. There was no evidence for the interchange between two disulfide linkages or between a disulfide linkage and a sulfhydryl group during the air-oxidation. The analysis of the products from the bifunctional polysarcosine showed that they were composed of a series of cyclic “monomer,” “dimer,” “trimer,” and higher “oligomers.” The cyclic structure was characterized by the larger elution volume in the gel chromatogram than that for a linear homologue having the same molecular weight. The weight fraction of each cyclic oligomer was determined by gel chromatography. The fraction of cyclic monomer F₁ decreased monotonously with increasing the chain length. Smaller values of F₁ were observed with cupric-ion catalyst than with ferric-ion catalyst. The dependence of F₁ on the polymer concentration was much smaller than that expected from a simple competition mechanism between intra- and intermolecular reactions. These results indicate that the choice between intra- and intermolecular reactions is governed by the mode of the coordination of sulfhydryl groups to transition metal ions.     

Characterization of two Synechococcus sp. PCC7002‐related cyanobacterial strains in relation to 16S rDNA,crtR gene,lipids and pigments

Two Synechococcus strains from the Culture Collection of the Institute for Marine Sciences of Andalusia (Cádiz, Spain), namely Syn01 and Syn02, were found to be closely related to the model strain Synechococcus sp. PCC7002 according to 16S rDNA (99% identity). Pigment and lipid profiles and crtR genes of these strains were ascertained and compared. The sequences of the crtR genes of these strains were constituted by 888 bp, and showed 99% identity between Syn01 and Syn02, and 94% identity of Syn01 and Syn02 to Synechococcus sp. PCC7002. There was coincidence in photosynthetic pigments between the three strains apart from the pigment synechoxanthin, which could be only observed in Synechococcus sp. PCC7002. Species of sulfoquinovosyl‐diacyl‐glycerol (SQDG), phosphatidyl‐glycerol (PG), mono‐ and di‐galactosyl‐diacyl‐glycerol (MGDG and DGDG) were detected by high performance liquid chromatography‐mass spectrometry analysis of lipid extracts. The most abundant species within each lipid class were those containing C18:3 together with C16:0 fatty acyl substituents in the glycerol backbone of the same molecule. From these results it is concluded that these cyanobacterial strains belong to group 2 of the lipid classification of cyanobacteria.     

Variable Sugar Fermentation by Clostridia

Forty-two sugar fermentation characteristics recorded as “d” in the 8th edition of Bergey's Manual of Determinative Bacteriology were reinvestigated by using eight different peptone media and 205 strains of nine species of pathogenic Clostridia. In the absence of sugar, the final pH of 7-day cultures in the basal medium varied widely depending on the peptone employed, the species tested, and even the strain of the species. In the presence of sugar, the final pH of 7-day cultures was markedly influenced by these factors. Since the sugars with reactions recorded as “d” were weakly fermented and, consequently, the fermentation reactions were easily affected by cultural variations resulting in strain instability, we employed the pH difference method (ΔpH method) in which the pH difference of 0.5 between cultures with and without sugar was used as the critical level. Thirty-six (86%) of the 42 sugar reactions recorded as “d” were sorted into “+” or “-” by the ΔpH method. Six sugars, however, still remained as “d” because of their extremely weak fermentation characters. The use of the ΔpH method in any peptone medium not only minimizes incorrect evaluation but also can provide some distinct criteria for identification of Clostridia.     

A comparison of the major lipid classes and fatty acid composition of marine unicellular cyanobacteria with freshwater species

The fatty acid composition of two motile (strains WH 8113 and WH 8103) and one nonmotile (strain WH 7803) marine cyanobacteria has been determined and compared with two freshwater unicellular Synechocystis species (strain PCC 6308 and PCC 6803). The fatty acid composition of lipid extracts of isolated membranes from Synechocystis PCC 6803 was found to be identical to that of whole cells. All the marine strains contained myristic acid (14:0) as the major fatty acid, with only traces of polyunsaturated fatty acids. This composition is similar to Synechocystis PCC 6308. The major lipid classes of the nonmotile marine strain were identified as digalactosyl diacylglycerol, monogalactosyl diacylglycerol, phosphatidylglycerol, and sulfoquinovosyl diacylglycerol, identical to those found in other cyanobacteria.Abbreviations DGDG Digalactosyl diacylglycerol - MGDG Monogalactosyldiacylglycerol - PG Phosphatidylglycerol - SGDG sulfoquinovosyl diacylglycerol - gc gas chromatography - ms mass spectrometry     

Helicobacter pylori outer inflammatory protein A (OipA) suppresses apoptosis of AGS gastric cells in vitro

Outer inflammatory protein A (OipA) is an important virulence factor associated with gastric cancer and ulcer development; however, the results have not been well established and turned out to be controversial. This study aims to elucidate the role of OipA in Helicobacter pylori infection using clinical strains harbouring oipA “on” and “off” motifs. Proteomics analysis was performed on AGS cell pre‐infection and postinfection with H. pylori oipA “on” and “off” strains, using liquid chromatography/mass spectrometry. AGS apoptosis and cell cycle assays were performed. Moreover, expression of vacuolating cytotoxin A (VacA) was screened using Western blotting. AGS proteins that have been suggested previously to play a role or associated with gastric disease were down‐regulated postinfection with oipA “off” strains comparing to oipA “on” strains. Furthermore, oipA “off” and ΔoipA cause higher level of AGS cells apoptosis and G0/G1 cell‐cycle arrest than oipA “on” strains. Interestingly, deletion of oipA increased bacterial VacA production. The capability of H. pylori to induce apoptosis and suppress expression of proteins having roles in human disease in the absence of oipA suggests that strains not expressing OipA may be less virulent or may even be protective against carcinogenesis compared those expressing OipA. This potentially explains the higher incidence of gastric cancer in East Asia where oipA “on” strains predominates.