Crystal structure and Hirshfeld surface analysis of a pyrrolo-thia-zine complex.

In the title compound, diethyl 2,2-dioxo-4-(thio-phen-2-yl)-1-[(thio-phen-2-yl)meth-yl]-3,4,6,7,8,8a-hexa-hydro-1H-pyrrolo-[2,1-c][1,4]thia-zine-1,3-di-carboxyl-ate, C22H28NO6S3, the pyrrolo ring is in an envelope conformation while the thia-zine ring adopts a near chair conformation. The dihedral angles between the thia-zine ring and the methyl-thienyl, thienyl and pyrrolo rings are 64.0 (2), 87.92 (7) and 5.6 (2)°, respectively. In the crystal, the mol-ecules are linked by weak C-H⋯O hydrogen bonds. A Hirshfeld surface analysis was performed to investigate the inter-molecular inter-actions. Disorder of the methyl-thienyl group with site occupancies of 0. 792 (3) and 0.208 (3) is observed.

Isomorphous diethyl 1-(4-chloro-benz-yl)-4-(4-chloro-phen-yl)-2,2-dioxo-3,4,6,7,8,8a-hexa-hydro-1H-pyrrolo-[2,1-c][1,4]thia-zine-1,3-di-carboxyl-ate and its 1-(4-methyl-benz-yl)-4-(4-methyl-phen-yl)-substituted analogue obeying the chloro-methyl exchange rule.

Accurate studies on the effect of substituents on the crystal packing are essential for understanding the inter-molecular inter-actions and thus paving the way to crystal structure prediction. The crystal structures of diethyl 1-(4-chloro-benz-yl)-4-(4-chloro-phen-yl)-2,2-dioxo-3,4,6,7,8,8a-hexa-hydro-1H-pyrrolo-[2,1-c][1,4]thiazine-1,3-di-carboxyl-ate, C26H29Cl2NO6S, (I), and its isomorphous pair diethyl 1-(4-methyl-benz-yl)-4-(4-methyl-phen-yl)-2,2-dioxo-3,4,6,7,8,8a-hexa-hydro-1H-pyrrolo-[2,1-c][1,4]thia-zine-1,3-di-carboxyl-ate, C28H35NO6S, (II), are described. The mol-ecular aggregation patterns appear to be strikingly similar despite changes in the substituents, with a Cl atom in (I) being replaced by a methyl group in (II). Inspite of the chemical modifications, the structures of (I) and (I) are isomorphous, isostructural and found to obey the chlorine-methyl exchange rule. Both the structures feature C-H⋯O hydrogen bonding. However, a distinguishing feature between (I) and (II) is observed in the conformation of the pyrrole rings where the twist occurs on different C-N bonds. Hirshfeld analysis of both structures is presented and discussed.

Toxicity assessment and screening of tetrodotoxin in the oblong blowfish (Takifugu oblongus) from the Tamil Nadu Coast of Bay of Bengal, India.

OBJECTIVE: To assess the toxicity of the pufferfish Takifugu oblongus, from Chennai coast, Tamil Nadu, India and to detect the presence of Tetrodotoxin (TTX). METHODS: The toxicity was evaluated by mouse bioassay using Swiss Albino mice which were expressed in mouse units (MU). Gross anatomical features were observed which is followed by histopathology of the dead mice tissues to establish the toxicity. Instrumental analysis for the presence of tetrodotoxin was also performed through GC-MS and HPLC. RESULTS: The toxicity of ovary was the maximum with 163 MU/g and lowest toxicity was observed in skin with 75.88 MU/g. Histopathological analyses of the dead mice showed various cellular degenerations and inflammations. The amount of Tetrodotoxin detected through GC-MS and HPLC was more reliable and sensitive than the customary mouse bioassay as instrumental analyses were able to detect even nanograms of the toxin. CONCLUSIONS: The present study evidently proved that Takifugu oblongus is highly toxic and consumption of the same can pose serious threat for health and possible lethality to humans.

Immunophenotypic comparison of heterogenous non-sorted versus sorted mononuclear cells from human umbilical cord blood: a novel cell enrichment approach.

Human umbilical cord blood (hUCB) has been the preferred source of stem cells for the treatment of haematological malignancies and genetic disorders. This is primarily due to its non-invasiveness, high accessibility with relative ease of isolation. Still failures do prevail due to its heterogeneity and lesser frequency of MSC identified in UCB. This study, thus, employs a cell enrichment technology to improve its therapeutic efficacy. This was achieved by immunophenotypic comparison of stem cells isolated from the heterogenous non-sorted mononuclear cells (MNCs), linage depleted (Lin+ and Lin-) fractions obtained from magnetic activated cell sorter (MACS) and sorted MNCs obtained by fluorescent activated cell sorter (FACS). The markers under consideration were CD29, CD44, CD34, CD45, CD133, CD90 and CD117. FACS sorted MNCs were rich in naive stem cell population, whereas non-sorted MNCs and lineage depleted fractions were found to be rich in progenitors. Thus, we suggest that a combination therapy of both sorted population might serve as an alternative valuable tool in treating haematologic/genetic disorders. However, further research on cell enrichment technology might give a clue for improved cell based therapy in regenerative medicine.

Lineage depletion of stromal vascular fractions isolated from human adipose tissue: a novel approach towards cell enrichment technology.

The therapeutic rationale for tissue repair and regeneration using stem cells is at its infancy and needs advancement in understanding the role of individual component's innate capability. As stem cells of adipose tissue reside in a more heterogeneous population of stromal vascular fractions, cell separation or sorting becomes an eminent step towards revealing their unique properties. This study elucidates the comparative efficacy of lineage depleted adipose derived stromal vascular fraction (SVF) and their innate ability using magnetic activated cell sorter (MACS). To this end, isolated SVF from human adipose tissue was lineage depleted according to the manufacturer's instructions using specific antibody cocktail through MACS. The enriched lineage negative (lin-) and lineage positive (lin+) cell fractions were cultured, phenotypically characterized for the panel of cell surface markers using flowcytometry and subjected to osteoblastic and adipogenic differentiation. The expression profile obtained for lin- cells was CD34-/CD45-/HLADR-/CD49d-/CD140b-/CD31-/CD90+/CD105+/CD73+/CD54+/CD166+/CD117- when compared to Lin+ cells expressing CD34+/CD45+/HLADR-/CD49d-/CD140b+/CD31-/CD90+/CD105+/CD73+/CD54+/CD166+/CD117+ (CD-cluster of differentiation). These results, thus, advances our understanding on the inherent property of the individual cell population. Furthermore, both the fractions exhibited mesodermal lineage differentiation capacity. To conclude, this research pursuit rationalized the regenerative therapeutic applicability of both lin- and lin+ cultures of human adipose tissue for disorders of mesodermal, haematological and vascular origin.

Comparison of feto-maternal organ derived stem cells in facets of immunophenotype, proliferation and differentiation.

Scientific explorations on feto-maternal organ stem cells revealed its possible applicability in treatment of various diseases. However, establishment of an ideal placental tissue stem cell source in regenerative application is inconclusive and arduous. Hence, this study aims to resolve this tribulation by comparison of mesenchymal stem cells (MSC) from fetal placenta - amniotic membrane (AM-MSC), chorionic plate (CP-MSC) tissue and the maternal placenta-Decidua (D-MSC), thereby facilitating the researchers to determine their pertinent source. The cells were expanded and scrutinized for expression profiling, proliferation and differentiation ability. Remarkable expressions of certain markers in addition to its prospective mesodermal differentiation confirmed their mesenchyme origin. Despite the specified alikeness among these sources, reliable and non-invasive procurement of AM-MSC coupled with its higher growth potency makes it the most constructive stem cell source. However, exhibited similarities demands further investigations on extensive expandability and cytogenetic stability of these sources prior to its therapeutic applicability.

Ethyl 3-(4-chloro-benzo-yl)-1-(4-chloro-benz-yl)-4-(4-chloro-phen-yl)-2,2-dioxo-3,4,6,7,8,8a-hexa-hydro-1H-pyrrolo-[2,1-c][1,4]thia-zine-1-carboxyl-ate.

In the title compound, C30H28Cl3NO5S, the pyrrolidine ring adopts an envelope conformation (with the N atom as the flap) and the thia-zine ring is in a distorted chair conformation. The mol-ecular structure shows three intra-molecular C-H⋯O inter-actions leading to self-associated ring S(6) and two S(7) motifs. In the crystal, the molecules are linked by C-H⋯O and C-H⋯Cl inter-actions. Two R 2 (2)(10) and one R 2 (2)(16) centrosymmetrically related ring motifs are observed in the unit cell and they are connected through C(6) and C(11) chain motifs extending along the b and c axes, respectively.

Prospective biomarkers of stem cells of human endometrium and fallopian tube compared with bone marrow.

The applicability of stem cells from the human endometrium and fallopian tube for regeneration is a fascinating area of research because of the role of these cells in dynamic tissue remodelling and their cyclical regenerative property during the menstrual cycle and pregnancy. Nevertheless, studies on the identity of biomarkers of these stem cells are limited and need to be extended. The present study has aimed at exploring the tissue-specific biomarkers of stem cells derived from the human endometrium and fallopian tube compared with those from bone marrow. Cells were isolated from human endometrium and fallopian tubes and characterized for biomarkers, including CD34, CD133, CD117, CD90, CD105, CD73, nestin, CD29, CD44, CD31, CD54, CD166, CD106, CD49d, CD45, ABCG2, SSEA4, OCT4, SOX2, CD140b and CD146, by flowcytometry. Both endometrium and fallopian tube sources exhibited positivity over a wide range of markers, as did bone marrow. In particular, they exhibited pluripotency, perivascular and mesenchymal stem cell markers and cell adhesion molecules, thereby suggesting their relevance in tissue repair and regeneration. Overall, the results of this study provide evidence for the presence of stem cells in the human endometrium and fallopian tube, which could thus represent additional stem cell sources for regenerative medicine.

Human omentum fat-derived mesenchymal stem cells transdifferentiates into pancreatic islet-like cluster.

Current protocols of islet cell transplantation for the treatment of diabetes mellitus have been hampered by islet availability and allograft rejection. Although bone marrow and subcutaneous adipose tissue stem cells feature their tissue repair efficacy, applicability of stem cells from various sources is being researched to develop a promising therapy for diabetes mellitus. Although omentum fat has emerged as an innovative source of stem cells, the dearth of researches confirming its transdifferentiation potential limits its applicability as a regenerative tool in diabetic therapy. Thus, this work is a maiden attempt to explore the colossal potency of omentum fat-derived stem cells on its lucrative differentiation ability. The plasticity of omentum fat stem cells was substantiated by transdifferentiation into pancreatic islet-like clusters, which was confirmed by dithizone staining and immunocytochemistry for insulin. It was also confirmed by the expression of pancreatic endocrine markers nestin and pancreatic duodenal homeobox 1 (Pdx 1) using Fluorescence-activated cell sorting (FACS), neurogenic 3, islet-1 transcription factor, paired box gene 4, Pdx 1 and insulin using quantitative real-time polymerase chain reaction and through insulin secretion assay. This study revealed the in vitro differentiation potency of omentum fat stem cells into pancreatic islet-like clusters. However, further research pursuits exploring its in vivo endocrine efficacy would make omentum fat stem cells a superior source for ß-cell replacement therapy.

Exploring the stem cell and non-stem cell constituents of human breast milk.

The immense potency of nutritional components of human breast milk and importance of breastfeeding is known worldwide. Recent researches had identified stem cells as integral component of human breast milk. Nevertheless, there is little proof of evidence on the stem cell constituents of breast milk. It is imperative to explore the cellular constituents of human breast milk, including of stem cells, to open new avenue in child's development and regeneration. Thus, we aimed at identifying the cellular constituents of human breast milk by phenotypic characterisation of diverse cell surface markers of hematopoietic stem cells (CD 34, CD 133, CD 117), mesenchymal stem cells (CD 90, CD 105, CD 73), myoepithelial cells (CD 29, CD 44), Immune cells (CD 209, CD 86, CD 83, CD 14, CD 13, HLADR, CD 45), as well as cell adhesion molecules (CD 31, CD 54, CD 166, CD 106, CD 49d), and other markers (ABCG2, CD140b) using flowcytometry. We found a lower expression of CD 34 (13.07 ± 2.0 %), CD 90 (7.79 ± 0.8 %) and CD 73 (2.19 ± 0.41 %), indicating scanty hematopoietic and mesenchymal stem cell population in human breast milk. On contrary, myoepithelial progenitors, cell adhesion molecules, immune cells and growth factors were identified as the major constituents of breast milk. Overall, this study illuminates the benefits of breast feeding as breast milk encompasses heterogeneous cellular components that benefits child's growth, immunity and development. However, further research on these constituents of human breast milk will widen their applicability in treatment of neonatal disorders.

Plasticity and banking potential of cultured adipose tissue derived mesenchymal stem cells.

The present day research on stem cells is yet not filled to the gunwales. The correlation of stem cell technology with tissue repair still has a long way to go. Since Embryonic stem cells are a kind of thorn inside when it comes to therapeutics, there emerged few potent contemporary sources of stem cells. Though bone marrow proves to be the pioneer among these, they lose themselves to adipose tissue in various aspects. The major shortcoming of bone marrow lies in lieu of its loss in potency with age. Adipose tissue puts up a tough competition among leading edge stem cell sources like cord blood and cord matrix. Adipose tissue wins over its counterparts in that it possesses astounding proliferation potency in vitro and holds a prominent stand in showcasing in vivo tissue repair efficacy. In spite of its precedence, the whole enchilada of adipose derived stem cells is still in its salad days. In our work we aim at excogitating the Mesenchymal stem cell population present in cultured adipose derived stem cells, in a wide perspective. Furthermore, the coalition of cell adhesion molecules with the proliferation potency of MSC and analysis of growth curve of ADSC was also paid accolade. The presence of robust MSC with immense differentiation and transdifferentiation potency was endorsed by lucrative differentiation of P3 cells into mesodermal and neuronal lineages. Additionally, mesenchymal stem cells exhibiting coherent expression of surface markers at P3 in all samples can be cryopreserved for therapeutic applications.

A comprehensive study on optimization of proliferation and differentiation potency of bone marrow derived mesenchymal stem cells under prolonged culture condition.

Bone marrow derived stem cells (BMSC) have paved way to clinical approaches for its utilization in a variety of diseases due to its ease of isolation combined with its multilineage differentiation capacity. However, the applicability of BMSC is not successful due to the lesser number of nucleated cells obtained from large samples. Hence, culture expansion of BMSC is a prerequisite, as high numbers of stem cells are needed to meet the standards of clinical advancement. There are attempts on optimizing culture condition for large scale production of BMSC. It was believed that, prolonged culture of BMSC is difficult since they tend to lose their characteristics and differentiation potential. Hence, our study aims to determine whether BMSCs could retain its proliferative and differentiation capacity in prolonged in vitro culture by a comparative study on extensive culturing of BMSC with the following four media, DMEM LG (DMEM-Low Glucose), DMEM KO (DMEM-Knock Out), Alpha MEM (Alpha Minimal Essential Medium), DMEM F 12. We found that two samples among the three cultured tend to lose their property in long term culturing. Besides, we also found that DMEM LG and Alpha MEM were the optimal media for in vitro culturing of BMSC. Overall, it was concluded that BMSC can be cultured until passage 15 without losing its characteristics. However, its potency beyond passage 15 has to be further elucidated for utilization of the ex vivo expanded BMSC for subsequent cellular therapies.

Effect of high glucose on extensive culturing of mesenchymal stem cells derived from subcutaneous fat, omentum fat and bone marrow.

Frontline research progresses the applicability of bone marrow and adipose tissue in regenerative medicine, but fails to account for the functional improvement of the diseased. The justification for the failure in terms of stem cell survival, proliferation and regeneration is unclear. However, hyperglycemia rising during pathological conditions might be one such stumbling block. The prevailing literature accounts for both detrimental and beneficial effect of high glucose on mesenchymal stem cells (MSCs) leading to perplexity. Thus, this study focuses on the effect of high glucose on mesenchymal stem cells derived from subcutaneous fat, omentum fat and bone marrow in extensive cultures. We provide evidence for the retention of MSC characteristics of all sources with regards to surface marker profiling, proliferation, differentiation and karyotyping when cultured extensively under DMEM-HG containing glucose concentration of 25 mmol.l(-1) . Thus, it can be concluded that hyperglycemia in vivo (11 mmol.l(-1) ) might not be a barrier for the ineffective functional improvement of transplanted stem cells. Furthermore, we elucidated subcutaneous and omentum fat as better sources of MSCs when compared with bone marrow, thereby making these sources optimal for therapies during hyperglycemic conditions. However, further research is needed to clear the path for efficient stem cell transplantation.

Unravelling the retention of proliferation and differentiation potency in extensive culture of human subcutaneous fat-derived mesenchymal stem cells in different media.

OBJECTIVES: This study has intended to investigate longevity of subcutaneous fat-derived mesenchymal stem cells (SF-MSCs) under extensive culturing. It has also focused on optimization of culture media for them over prolonged periods in vitro. MATERIALS AND METHODS: We evaluated SF-MSCs with reference to phenotypic characterization, proliferative ability, karyotype stability and differentiation potency with early (P3) and late passage (P20) conditions, using four different media, DMEM-LG, ALPHA-MEM, DMEM-F12 and DMEM-KO. RESULTS: This study unravels retention of SF-MSC characteristics in facets of phenotypic expression profile (CD 90, CD 105, CD 73, CD 34, CD 29, CD 54, CD 49d, CD 117, HLA-DR, CD 166, CD 31, CD 44), proliferative characteristics, karyotyping and differentiation potency prolonged culturing to P25 in all media. Population doubling time (PDT) in Alpha MEM, DMEM LG, DMEM F 12, DMEM KO were identified to be (1.81, 1.84, 1.9, 2.08 days) at early passage and (2.93, 2.94, 3.12, 3.06 days) at late passage. As a corollary, Alpha MEM and DMEM LG serve as appropriate basal media for SF-MSC when proliferative potency is considered. CONCLUSIONS: In research, it is imperative that SF-MSC uphold their expansion potency in the aforesaid attributes in all media over extensive culturing, thereby transforming their colossal in vitro potency, with the aim of curing a wide horizon of diseases.

Comparison of the levels of the growth factors in umbilical cord serum and human milk and its clinical significance.

The process of the growth of the fetus begins in the uterus and gets further accelerated following the birth, especially during initial few months. The role of the growth factors in the physiology of the cellular growth is already well established. Vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) seem to be imperative for angiogenesis, cell development and proliferation as well as maintenance of the tissues. The levels of these factors in the maternal serum during pregnancy as well as during postpartum period are insignificant. Consequently, we hypothesized that the fetus receives moderate supply of these growth factors from the placenta during its stay in the uterus. This supply gets further augmented during the postpartum period through the different source, i.e. mother's milk. To study this physiological transition of the source of the growth factors from the placenta to the breast milk, the concentrations of VEGF and HGF in the cord serum of full term neonates and that in the breast milk of the corresponding mothers were analyzed during ELISA. The human milk, especially the colostrum revealed significantly higher levels of VEGF and HGF (1541.759 ± 119.349 pg/ml and 7129.249 ± 273.472 pg/ml) than cord serum (16.632 ± 0.773 pg/ml and 2581.6 ± 108.275 pg/ml) respectively. The multifold higher levels of VEGF observed in colostrum probably correlates with its high neonatal requirement for the maturation of the gastrointestinal epithelium following birth. The higher levels of both the growth factors in the breast milk than those observed in the cord serum probably explain their higher needs by the neonates for immunological protection, protein synthesis and neurocognitive development. The observations of the present study strengthen the policy of the colostrum feeding, which is promoted by organizations like World Health Organization (WHO). This study further documents the fact that the commercial milk formulae cannot replace the human milk.

Septal localization of the Mycobacterium tuberculosis MtrB sensor kinase promotes MtrA regulon expression.

The mechanisms responsible for activation of the MtrAB two-component regulatory signal transduction system, which includes sensor kinase MtrB and response regulator MtrA, are unknown. Here, we show that an MtrB-GFP fusion protein localized to the cell membrane, the septa, and the poles in Mycobacterium tuberculosis and Mycobacterium smegmatis. This localization was independent of MtrB phosphorylation status but dependent upon the assembly of FtsZ, the initiator of cell division. The M. smegmatis mtrB mutant was filamentous, defective for cell division, and contained lysozyme-sensitive cell walls. The mtrB phenotype was complemented by either production of MtrB protein competent for phosphorylation or overproduction of MtrA(Y102C) and MtrA(D13A) mutant proteins exhibiting altered phosphorylation potential, indicating that either MtrB phosphorylation or MtrB independent expression of MtrA regulon genes, including those involved in cell wall processing, are necessary for regulated cell division. In partial support of this observation, we found that the essential cell wall hydrolase ripA is an MtrA target and that the expression of bona fide MtrA targets ripA, fbpB, and dnaA were compromised in the mtrB mutant and partially rescued upon MtrA(Y102C) and MtrA(D13A) overproduction. MtrB septal assembly was compromised upon FtsZ depletion and exposure of cells to mitomycin C, a DNA damaging agent, which interferes with FtsZ ring assembly. Expression of MtrA targets was also compromised under the above conditions, indicating that MtrB septal localization and MtrA regulon expression are linked. We propose that MtrB septal association is a necessary feature of MtrB activation that promotes MtrA phosphorylation and MtrA regulon expression.

Surface antigenic profiling of stem cells from human omentum fat in comparison with subcutaneous fat and bone marrow.

Omentum fat derived stem cells have emerged as an alternative and accessible therapeutic tool in recent years in contrast to the existing persuasive sources of stem cells, bone marrow and subcutaneous adipose tissue. However, there has been a scanty citation on human omentum fat derived stem cells. Furthermore, identification of specific cell surface markers among aforesaid sources is still controversial. In lieu of this existing perplexity, the current research work aims at signifying omentum fat as a ground-breaking source of stem cells by surface antigenic profiling of stem cell population. In this study, we examined and compared the profiling of cell surface antigenic expressions of hematopoietic stem cells, mesenchymal stem cells, cell adhesion molecules and other unique markers such as ABCG2, ALDH and CD 117 in whole cell population of human omentum fat, subcutaneous fat and bone marrow. The phenotypic characterization through flowcytometry revealed the positive expressions of CD 34, CD 45, CD 133, HLADR, CD 90, CD 105, CD 73, CD 29, CD 13, CD 44, CD 54, CD 31, ALDH and CD 117 in all sources. The similarities between the phenotypic expressions of omentum fat derived stem cells to that of subcutaneous fat and bone marrow substantiates that identification of ultimate source for curative therapeutics is arduous to assess. Nevertheless, these results support the potential therapeutic application of omentum fat derived stem cells.

Diethyl 1-benzyl-2,2-dioxo-4-phenyl-3,4,6,7,8,8a-hexa-hydro-1H-pyrrolo-[2,1-c][1,4]thia-zine-1,3-dicarboxyl-ate.

In the title compound, C(26)H(31)NO(6)S, the five-membered pyrrolidine ring adopts an envelope conformation and the six-membered thia-zine ring is in a distorted chair conformation. The crystal packing is stabilized through an inter-molecular C-H⋯O inter-action, generating inversion-related R(2) (2)(10) ring motifs.

ChiZ levels modulate cell division process in mycobacteria.

We have previously shown that expression of chiZ (Rv2719c), encoding a cell wall hydrolase, is upregulated in response to DNA damaging agents and exposure to cephalexin. Furthermore, increased levels of ChiZ lead to decreased viability, loss of membrane integrity and defects in FtsZ-GFP localization and cell division. We now show that ChiZ N'-terminal 110 amino acid region, containing the cell wall hydrolase activity, is sufficient to modulate FtsZ-GFP localization. Further, we found that FtsZ-GFP rings are stabilized in a chiZ deletion strain indicating that ChiZ activity regulates FtsZ assembly. Overexpression of ftsZ did not reverse the reduction in viability caused by overproduction of ChiZ indicating that ChiZ neither interacts with nor directly influences FtsZ assembly. Bacterial two-hybrid assays revealed that ChiZ interacts with FtsI and FtsQ, two other septasomal proteins, but not with FtsZ. Finally, we show that ChiZ is not required for virulence of Mycobacterium tuberculosis in murine macrophages and mice. Our data suggest that optimal levels and activity of the cell wall hydrolase ChiZ are required for regulated cell division in mycobacteria.

Control of CydB and GltA1 expression by the SenX3 RegX3 two component regulatory system of Mycobacterium tuberculosis.

Two component regulatory systems are used widely by bacteria to coordinate changes in global gene expression profiles in response to environmental signals. The SenX3-RegX3 two component system of Mycobacterium tuberculosis has previously been shown to play a role in virulence and phosphate-responsive control of gene expression. We demonstrate that expression of SenX3-RegX3 is controlled in response to growth conditions, although the absolute changes are small. Global gene expression profiling of a RegX3 deletion strain and wild-type strain in different culture conditions (static, microaerobic, anaerobic), as well as in an over-expressing strain identified a number of genes with changed expression patterns. Among those were genes previously identified as differentially regulated in aerobic culture, including ald (encoding alanine dehydrogenase) cyd,encoding a subunit of the cytochrome D ubiquinol oxidase, and gltA1, encoding a citrate synthase. Promoter activity in the upstream regions of both cydB and gltA1 was altered in the RegX3 deletion strain. DNA-binding assays confirmed that RegX3 binds to the promoter regions of ald, cydB and gltA1 in a phosphorylation-dependent manner. Taken together these data suggest a direct role for the SenX-RegX3 system in modulating expression of aerobic respiration, in addition to its role during phosphate limitation.