scholarly journals Cyclic Dinucleotide-Controlled Regulatory Pathways in Streptomyces Species

2015 ◽  
Vol 198 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Natalia Tschowri
Keyword(s):  
Cell Wall ◽  
Current Knowledge ◽  
Second Messengers ◽  
Streptomyces Species ◽  
Content Type ◽  
Regulatory Pathways ◽  
Cellular Processes ◽  
Signal Transduction Networks ◽  
Cyclic Dinucleotides ◽  
Cyclic Dinucleotide

The cyclic dinucleotides cyclic 3′,5′-diguanylate (c-di-GMP) and cyclic 3′,5′-diadenylate (c-di-AMP) have emerged as key components of bacterial signal transduction networks. These closely related second messengers follow the classical general principles of nucleotide signaling by integrating diverse signals into regulatory pathways that control cellular responses to changing environments. They impact distinct cellular processes, with c-di-GMP having an established role in promoting bacterial adhesion and inhibiting motility and c-di-AMP being involved in cell wall metabolism, potassium homeostasis, and DNA repair. The involvement of c-dinucleotides in the physiology of the filamentous, nonmotile streptomycetes remained obscure until recent discoveries showed that c-di-GMP controls the activity of the developmental master regulator BldD and that c-di-AMP determines the level of the resuscitation-promoting factor A(RpfA) cell wall-remodelling enzyme. Here, I summarize our current knowledge of c-dinucleotide signaling inStreptomycesspecies and highlight the important roles of c-di-GMP and c-di-AMP in the biology of these antibiotic-producing, multicellular bacteria.

scholarly journals Hanks-Type Serine/Threonine Protein Kinases and Phosphatases in Bacteria: Roles in Signaling and Adaptation to Various Environments

2018 ◽  
Vol 19 (10) ◽  
pp. 2872 ◽  
Author(s):  
Monika Janczarek ◽  
José-María Vinardell ◽  
Paulina Lipa ◽  
Magdalena Karaś
Keyword(s):  
Dna Binding ◽  
Essential Role ◽  
Current Knowledge ◽  
Response Regulator ◽  
Protein Targets ◽  
Regulatory Pathways ◽  
Translational Machinery ◽  
Signaling Systems ◽  
Cellular Processes ◽  
Division Cell

Reversible phosphorylation is a key mechanism that regulates many cellular processes in prokaryotes and eukaryotes. In prokaryotes, signal transduction includes two-component signaling systems, which involve a membrane sensor histidine kinase and a cognate DNA-binding response regulator. Several recent studies indicate that alternative regulatory pathways controlled by Hanks-type serine/threonine kinases (STKs) and serine/threonine phosphatases (STPs) also play an essential role in regulation of many different processes in bacteria, such as growth and cell division, cell wall biosynthesis, sporulation, biofilm formation, stress response, metabolic and developmental processes, as well as interactions (either pathogenic or symbiotic) with higher host organisms. Since these enzymes are not DNA-binding proteins, they exert the regulatory role via post-translational modifications of their protein targets. In this review, we summarize the current knowledge of STKs and STPs, and discuss how these enzymes mediate gene expression in prokaryotes. Many studies indicate that regulatory systems based on Hanks-type STKs and STPs play an essential role in the regulation of various cellular processes, by reversibly phosphorylating many protein targets, among them several regulatory proteins of other signaling cascades. These data show high complexity of bacterial regulatory network, in which the crosstalk between STK/STP signaling enzymes, components of TCSs, and the translational machinery occurs. In this regulation, the STK/STP systems have been proved to play important roles.

scholarly journals The Ser/Thr Kinase PrkC Participates in Cell Wall Homeostasis and Antimicrobial Resistance inClostridium difficile

2019 ◽  
Vol 87 (8) ◽  
Author(s):  
Elodie Cuenot ◽  
Transito Garcia-Garcia ◽  
Thibaut Douche ◽  
Olivier Gorgette ◽  
Pascal Courtin ◽  
...  
Keyword(s):  
Cell Wall ◽  
Type Strain ◽  
Wild Type Strain ◽  
Cell Envelope ◽  
Wild Type ◽  
Hamster Model ◽  
Content Type ◽  
Physiological Processes ◽  
Signal Transduction Networks ◽  
Mean Size

ABSTRACTClostridium difficileis the leading cause of antibiotic-associated diarrhea in adults. During infection,C. difficilemust detect the host environment and induce an appropriate survival strategy. Signal transduction networks involving serine/threonine kinases (STKs) play key roles in adaptation, as they regulate numerous physiological processes. PrkC ofC. difficileis an STK with two PASTA domains. We showed that PrkC is membrane associated and is found at the septum. We observed that deletion ofprkCaffects cell morphology with an increase in mean size, cell length heterogeneity, and presence of abnormal septa. A ΔprkCmutant was able to sporulate and germinate but was less motile and formed more biofilm than the wild-type strain. Moreover, a ΔprkCmutant was more sensitive to antimicrobial compounds that target the cell envelope, such as the secondary bile salt deoxycholate, cephalosporins, cationic antimicrobial peptides, and lysozyme. This increased susceptibility was not associated with differences in peptidoglycan or polysaccharide II composition. However, the ΔprkCmutant had less peptidoglycan and released more polysaccharide II into the supernatant. A proteomic analysis showed that the majority ofC. difficileproteins associated with the cell wall were less abundant in the ΔprkCmutant than the wild-type strain. Finally, in a hamster model of infection, the ΔprkCmutant had a colonization delay that did not significantly affect overall virulence.

scholarly journals Progress in Understanding the Molecular Basis Underlying Functional Diversification of Cyclic Dinucleotide Turnover Proteins

2016 ◽  
Vol 199 (5) ◽  
Author(s):  
Ute Römling ◽  
Zhao-Xun Liang ◽  
J. Maxwell Dow
Keyword(s):  
Molecular Basis ◽  
Current Knowledge ◽  
Second Messenger ◽  
Diguanylate Cyclase ◽  
Structural Variations ◽  
Functional Diversification ◽  
Cyclic Dinucleotides ◽  
Signaling Domains ◽  
Synthesis And Degradation ◽  
Cyclic Dinucleotide

ABSTRACT Cyclic di-GMP was the first cyclic dinucleotide second messenger described, presaging the discovery of additional cyclic dinucleotide messengers in bacteria and eukaryotes. The GGDEF diguanylate cyclase (DGC) and EAL and HD-GYP phosphodiesterase (PDE) domains conduct the turnover of cyclic di-GMP. These three unrelated domains belong to superfamilies that exhibit significant variations in function, and they include both enzymatically active and inactive members, with a subset involved in synthesis and degradation of other cyclic dinucleotides. Here, we summarize current knowledge of sequence and structural variations that underpin the functional diversification of cyclic di-GMP turnover proteins. Moreover, we highlight that superfamily diversification is not restricted to cyclic di-GMP signaling domains, as particular DHH/DHHA1 domain and HD domain proteins have been shown to act as cyclic di-AMP phosphodiesterases. We conclude with a consideration of the current limitations that such diversity of action places on bioinformatic prediction of the roles of GGDEF, EAL, and HD-GYP domain proteins.

scholarly journals An Essential Poison: Synthesis and Degradation of Cyclic Di-AMP in Bacillus subtilis

2015 ◽  
Vol 197 (20) ◽  
pp. 3265-3274 ◽  
Author(s):  
Jan Gundlach ◽  
Felix M. P. Mehne ◽  
Christina Herzberg ◽  
Jan Kampf ◽  
Oliver Valerius ◽  
...  
Keyword(s):  
Cell Wall ◽  
Bacillus Subtilis ◽  
Nitrogen Source ◽  
Second Messengers ◽  
Regulatory Protein ◽  
Control Cell ◽  
Model Organism ◽  
Second Messenger ◽  
Content Type ◽  
Gram Positive Bacteria

ABSTRACTGram-positive bacteria synthesize the second messenger cyclic di-AMP (c-di-AMP) to control cell wall and potassium homeostasis and to secure the integrity of their DNA. In the firmicutes, c-di-AMP is essential for growth. The model organismBacillus subtilisencodes three diadenylate cyclases and two potential phosphodiesterases to produce and degrade c-di-AMP, respectively. Among the three cyclases, CdaA is conserved in nearly all firmicutes, and this enzyme seems to be responsible for the c-di-AMP that is required for cell wall homeostasis. Here, we demonstrate that CdaA localizes to the membrane and forms a complex with the regulatory protein CdaR and the glucosamine-6-phosphate mutase GlmM. Interestingly,cdaA,cdaR, andglmMform a gene cluster that is conserved throughout the firmicutes. This conserved arrangement and the observed interaction between the three proteins suggest a functional relationship. Our data suggest that GlmM and GlmS are involved in the control of c-di-AMP synthesis. These enzymes convert glutamine and fructose-6-phosphate to glutamate and glucosamine-1-phosphate. c-di-AMP synthesis is enhanced if the cells are grown in the presence of glutamate compared to that in glutamine-grown cells. Thus, the quality of the nitrogen source is an important signal for c-di-AMP production. In the analysis of c-di-AMP-degrading phosphodiesterases, we observed that both phosphodiesterases, GdpP and PgpH (previously known as YqfF), contribute to the degradation of the second messenger. Accumulation of c-di-AMP in agdpP pgpHdouble mutant is toxic for the cells, and the cells respond to this accumulation by inactivation of the diadenylate cyclase CdaA.IMPORTANCEBacteria use second messengers for signal transduction. Cyclic di-AMP (c-di-AMP) is the only second messenger known so far that is essential for a large group of bacteria. We have studied the regulation of c-di-AMP synthesis and the role of the phosphodiesterases that degrade this second messenger. c-di-AMP synthesis strongly depends on the nitrogen source: glutamate-grown cells produce more c-di-AMP than glutamine-grown cells. The accumulation of c-di-AMP in a strain lacking both phosphodiesterases is toxic and results in inactivation of the diadenylate cyclase CdaA. Our results suggest that CdaA is the critical diadenylate cyclase that produces the c-di-AMP that is both essential and toxic upon accumulation.

scholarly journals Overexpression or Deletion of Ergosterol Biosynthesis Genes Alters Doubling Time, Response to Stress Agents, and Drug Susceptibility inSaccharomyces cerevisiae

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Somanon Bhattacharya ◽  
Brooke D. Esquivel ◽  
Theodore C. White
Keyword(s):  
Cell Wall ◽  
Drug Targets ◽  
Doubling Time ◽  
Gene Deletion ◽  
Drug Susceptibility ◽  
Ergosterol Biosynthesis ◽  
Gene Overexpression ◽  
Content Type ◽  
Cellular Processes ◽  
Erg Genes

ABSTRACTErgosterol (ERG) is a critical sterol in the cell membranes of fungi, and its biosynthesis is tightly regulated by 25 known enzymes along the ERG production pathway. The effects of changes in expression of each ERG biosynthesis enzyme inSaccharomyces cerevisiaewere analyzed by the use of gene deletion or plasmid-borne overexpression constructs. The strains overexpressing the ERG pathway genes were examined for changes in doubling time and responses to a variety of stress agents. In addition, ERG gene overexpression strains and ERG gene deletion strains were tested for alterations in antifungal drug susceptibility. The data show that disruptions in ergosterol biosynthesis regulation can affect a diverse set of cellular processes and can cause numerous phenotypic effects. Some of the phenotypes observed include dramatic increases in doubling times, respiratory deficiencies on glycerol media, cell wall insufficiencies on Congo red media, and disrupted ion homeostasis under iron or calcium starvation conditions. Overexpression or deletion of specific enzymes in the ERG pathway causes altered susceptibilities to a variety of classes of antifungal ergosterol inhibitors, including fluconazole, fenpropimorph, lovastatin, nystatin, amphotericin B, and terbinafine. This analysis of the effect of perturbations to the ERG pathway caused by systematic overexpression of each of the ERG pathway genes contributes significantly to the understanding of the ergosterol biosynthetic pathway and its relationship to stress response and basic biological processes. The data indicate that precise regulation of ERG genes is essential for cellular homeostasis and identify several ERG genes that could be exploited in future antifungal development efforts.IMPORTANCEA common target of antifungal drug treatment is the fungal ergosterol biosynthesis pathway. This report helps to identify ergosterol biosynthesis enzymes that have not previously been appreciated as drug targets. The effects of overexpression of each of the 25 ERG genes inS. cerevisiaewere analyzed in the presence of six stress agents that target essential cellular processes (cell wall biosynthesis, protein translation, respiration, osmotic/ionic stress, and iron and calcium homeostasis), as well as six antifungal inhibitors that target ergosterol biosynthesis. The importance of identifying cell perturbations caused by gene overexpression or deletion is emphasized by the prevalence of gene expression alterations in many pathogenic and drug-resistant clinical isolates. Genes whose altered expression causes the most extensive phenotypic alterations in the presence of stressors or inhibitors have the potential to be drug targets.

scholarly journals NrnA is a linear dinucleotide phosphodiesterase with limited function in cyclic dinucleotide metabolism in Listeria monocytogenes

2021 ◽  
Author(s):  
Aaron R. Gall ◽  
Brian Y. Hsueh ◽  
Cheta Siletti ◽  
Christopher M. Waters ◽  
TuAnh N. Huynh
Keyword(s):  
Listeria Monocytogenes ◽  
Mammalian Cells ◽  
Cell Infection ◽  
Cellular Processes ◽  
Hydrolytic Activities ◽  
Limited Function ◽  
Cyclic Dinucleotides ◽  
Virulence Regulator ◽  
Cyclic Dinucleotide

Listeria monocytogenes produces both c-di-AMP and c-di-GMP to mediate many important cellular processes, but the levels of both nucleotides must be regulated. C-di-AMP accumulation attenuates virulence and diminishes stress response, and c-di-GMP accumulation impairs bacterial motility. An important regulatory mechanism to maintain c-di-AMP and c-di-GMP homeostasis is to hydrolyze them to the linear dinucleotides pApA and pGpG, respectively, but the fates of these hydrolytic products have not been examined in L. monocytogenes . We found that NrnA, a stand-alone DHH-DHHA1 phosphodiesterase, has a broad substrate range, but with a strong preference for linear dinucleotides over cyclic dinucleotides. Although NrnA exhibited detectable cyclic dinucleotide hydrolytic activities in vitro, NrnA had negligible effects on their levels in the bacterial cell, even in the absence of the c-di-AMP phosphodiesterases PdeA and PgpH. The Δ nrnA mutant had a mammalian cell infection defect that was fully restored by E. coli Orn. Together, our data indicate that L. monocytogenes NrnA is functionally orthologous to Orn, and its preferred physiological substrates are most likely linear dinucleotides. Furthermore, our findings revealed that, unlike some other c-di-AMP and c-di-GMP-producing bacteria, L. monocytogenes does not employ their hydrolytic products to regulate their phosphodiesterases, at least at the pApA and pGpG levels in the Δ nrnA mutant. Finally, the Δ nrnA infection defect was overcome by constitutive activation of PrfA, the master virulence regulator, suggesting that accumulated linear dinucleotides might inhibit the expression, stability, or function of PrfA-regulated virulence factors. IMPORTANCE Listeria monocytogenes produces both c-di-AMP and c-di-GMP, and encodes specific phosphodiesterases that degrade them into pApA and pGpG, respectively, but the metabolism of these products has not been characterized in this bacterium. We found that L. monocytogenes NrnA degrades a broad range of nucleotides. Among the tested cyclic and linear substrates, it exhibits a strong biochemical and physiological preference the linear dinucleotides pApA, pGpG, and pApG. Unlike in some other bacteria, these oligoribonucleotides do not appear to interfere with cyclic dinucleotide hydrolysis. The absence of NrnA is well tolerated by L. monocytogenes in broth cultures but impairs its ability to infect mammalian cells. These findings indicate a separation of cyclic dinucleotide signaling and oligoribonucleotide metabolism in L. monocytogenes .

scholarly journals The Trk Potassium Transporter Is Required for RsmB-Mediated Activation of Virulence in the Phytopathogen Pectobacterium wasabiae

2015 ◽  
Vol 198 (2) ◽  
pp. 248-255 ◽  
Author(s):  
Rita S. Valente ◽  
Karina B. Xavier
Keyword(s):  
Cell Wall ◽  
Environmental Factor ◽  
Plant Cell ◽  
Plant Pathogen ◽  
Plant Cell Wall ◽  
Cell Wall Degrading Enzymes ◽  
Content Type ◽  
Regulatory Pathways ◽  
Potassium Transporter ◽  
Degrading Enzymes

ABSTRACTPectobacterium wasabiae(previously known asErwinia carotovora) is an important plant pathogen that regulates the production of plant cell wall-degrading enzymes through anN-acyl homoserine lactone-based quorum sensing system and through the GacS/GacA two-component system (also known as ExpS/ExpA). At high cell density, activation of GacS/GacA induces the expression of RsmB, a noncoding RNA that is essential for the activation of virulence in this bacterium. A genetic screen to identify regulators of RsmB revealed that mutants defective in components of a putative Trk potassium transporter (trkHandtrkA) had decreasedrsmBexpression. Further analysis of these mutants showed that changes in potassium concentration influencedrsmBexpression and consequent tissue damage in potato tubers and that this regulation required an intact Trk system. Regulation ofrsmBexpression by potassium via the Trk system occurred even in the absence of the GacS/GacA system, demonstrating that these systems act independently and are both required for full activation of RsmB and for the downstream induction of virulence in potato infection assays. Overall, our results identified potassium as an essential environmental factor regulating the Rsm system, and the consequent induction of virulence, in the plant pathogenP. wasabiae.IMPORTANCECrop losses from bacterial diseases caused by pectolytic bacteria are a major problem in agriculture. By studying the regulatory pathways involved in controlling the expression of plant cell wall-degrading enzymes inPectobacterium wasabiae, we showed that the Trk potassium transport system plays an important role in the regulation of these pathways. The data presented further identify potassium as an important environmental factor in the regulation of virulence in this plant pathogen. We showed that a reduction in virulence can be achieved by increasing the extracellular concentration of potassium. Therefore, this work highlights how elucidation of the mechanisms involved in regulating virulence can lead to the identification of environmental factors that can influence the outcome of infection.

scholarly journals DncV Synthesizes Cyclic GMP-AMP and Regulates Biofilm Formation and Motility inEscherichia coliECOR31

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Fengyang Li ◽  
Annika Cimdins ◽  
Manfred Rohde ◽  
Lothar Jänsch ◽  
Volkhard Kaever ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Cyclic Gmp ◽  
Life Style ◽  
Biofilm Formation ◽  
Second Messengers ◽  
Content Type ◽  
E Coli ◽  
Physiological Processes ◽  
Cyclic Dinucleotides ◽  
El Tor

ABSTRACTCyclic dinucleotides (cDNs) act as intracellular second messengers, modulating bacterial physiology to regulate the fundamental life style transition between motility and sessility commonly known as biofilm formation. Cyclic GMP-AMP (cGAMP), synthesized by the dinucleotide cyclase DncV, is a newly discovered cDN second messenger involved in virulence and chemotaxis inVibrio choleraeO1 biovar El Tor. Here we report a novel role for horizontally transferred DncV in cGAMP production and regulation of biofilm formation and motility in the animal commensal strainEscherichia coliECOR31. ECOR31 expresses a semiconstitutive temperature-independent rdar (red,dry,andrough) morphotype on Congo red agar plates characterized by the extracellular matrix components cellulose and curli fimbriae which requires activation by the major biofilm regulator CsgD and cyclic di-GMP signaling. In contrast, C-terminal His-tagged DncV negatively regulates the rdar biofilm morphotype and cell aggregation via downregulation ofcsgDmRNA steady-state level. Furthermore, DncV sequentially promotes and inhibits adhesion to the abiotic surface after 24 h and 48 h of growth, respectively. DncV also suppresses swimming and swarming motility posttranscriptional of the class 1 flagellum regulon geneflhD. Purified DncV produced different cDNs, cyclic di-GMP, cyclic di-AMP, an unknown product(s), and the dominant species 3′3′-cGAMP.In vivo, only the 3′3′-cGAMP concentration was elevated upon short-term overexpression ofdncV, making this work a first report on cGAMP production inE. coli. Regulation of rdar biofilm formation and motility upon overexpression of untagged DncV in combination with three adjacent cotransferred gene products suggests a novel temperature-dependent cGAMP signaling module inE. coliECOR31.IMPORTANCEThe ability of bacteria to sense and respond to environmental signals is critical for survival. Bacteria use cyclic dinucleotides as second messengers to regulate a number of physiological processes, such as the fundamental life style transition between motility and sessility (biofilm formation). cGAMP, which is synthesized by a dinucleotide cyclase called DncV, is a newly discovered second messenger involved in virulence and chemotaxis in theVibrio choleraebiovar El Tor causing the current 7th cholera pandemic. However, to what extent cGAMP exists and participates in physiological processes in other bacteria is still unknown. In this study, we found an elevated cGAMP level to possibly regulate biofilm formation and motility in the animal commensalE. colistrain ECOR31. Thus, we detected a novel role for cGAMP signaling in regulation of physiological processes other than those previously reported in proteobacterial species.

scholarly journals Plasmodium Helical Interspersed Subtelomeric (PHIST) Proteins, at the Center of Host Cell Remodeling

2016 ◽  
Vol 80 (4) ◽  
pp. 905-927 ◽  
Author(s):  
Jan D. Warncke ◽  
Ioannis Vakonakis ◽  
Hans-Peter Beck
Keyword(s):  
Host Cell ◽  
Current Knowledge ◽  
Surface Display ◽  
Protein Family ◽  
Content Type ◽  
Cellular Processes ◽  
Cell Remodeling ◽  
Definition Of ◽  
Few Data ◽  
Available Information

SUMMARYDuring the asexual cycle,Plasmodium falciparumextensively remodels the human erythrocyte to make it a suitable host cell. A large number of exported proteins facilitate this remodeling process, which causes erythrocytes to become more rigid, cytoadherent, and permeable for nutrients and metabolic products. Among the exported proteins, a family of 89 proteins, called thePlasmodiumhelical interspersed subtelomeric (PHIST) protein family, has been identified. While also found in otherPlasmodiumspecies, the PHIST family is greatly expanded inP. falciparum. Although a decade has passed since their first description, to date, most PHIST proteins remain uncharacterized and are of unknown function and localization within the host cell, and there are few data on their interactions with other host or parasite proteins. However, over the past few years, PHIST proteins have been mentioned in the literature at an increasing rate owing to their presence at various localizations within the infected erythrocyte. Expression of PHIST proteins has been implicated in molecular and cellular processes such as the surface display of PfEMP1, gametocytogenesis, changes in cell rigidity, and also cerebral and pregnancy-associated malaria. Thus, we conclude that PHIST proteins are central to host cell remodeling, but despite their obvious importance in pathology, PHIST proteins seem to be understudied. Here we review current knowledge, shed light on the definition of PHIST proteins, and discuss these proteins with respect to their localization and probable function. We take into consideration interaction studies, microarray analyses, or data from blood samples from naturally infected patients to combine all available information on this protein family.

scholarly journals Regulation of Growth, Cell Shape, Cell Division, and Gene Expression by Second Messengers (p)ppGpp and Cyclic Di-GMP in Mycobacterium smegmatis

2016 ◽  
Vol 198 (9) ◽  
pp. 1414-1422 ◽  
Author(s):  
Kuldeepkumar Ramnaresh Gupta ◽  
Priyanka Baloni ◽  
Shantinath S. Indi ◽  
Dipankar Chatterji
Keyword(s):  
Gene Expression ◽  
Electron Microscopy ◽  
Cell Wall ◽  
Cell Division ◽  
Mycobacterium Smegmatis ◽  
Biofilm Formation ◽  
Second Messengers ◽  
Antibiotic Sensitivity ◽  
Cell Length ◽  
Content Type

ABSTRACTThe alarmone (p)ppGpp regulates transcription, translation, replication, virulence, lipid synthesis, antibiotic sensitivity, biofilm formation, and other functions in bacteria. Signaling nucleotide cyclic di-GMP (c-di-GMP) regulates biofilm formation, motility, virulence, the cell cycle, and other functions. InMycobacterium smegmatis, both (p)ppGpp and c-di-GMP are synthesized and degraded by bifunctional proteins RelMsmand DcpA, encoded byrelMsmanddcpAgenes, respectively. We have previously shown that the ΔrelMsmand ΔdcpAknockout strains are antibiotic resistant and defective in biofilm formation, show altered cell surface properties, and have reduced levels of glycopeptidolipids and polar lipids in their cell wall (K. R. Gupta, S. Kasetty, and D. Chatterji, Appl Environ Microbiol 81:2571–2578, 2015,http://dx.doi.org/10.1128/AEM.03999-14). In this work, we have explored the phenotypes that are affected by both (p)ppGpp and c-di-GMP in mycobacteria. We have shown that both (p)ppGpp and c-di-GMP are needed to maintain the proper growth rate under stress conditions such as carbon deprivation and cold shock. Scanning electron microscopy showed that low levels of these second messengers result in elongated cells, while high levels reduce the cell length and embed the cells in a biofilm-like matrix. Fluorescence microscopy revealed that the elongated ΔrelMsmand ΔdcpAcells are multinucleate, while transmission electron microscopy showed that the elongated cells are multiseptate. Gene expression analysis also showed that genes belonging to functional categories such as virulence, detoxification, lipid metabolism, and cell-wall-related processes were differentially expressed. Our results suggests that both (p)ppGpp and c-di-GMP affect some common phenotypes inM. smegmatis, thus raising a possibility of cross talk between these two second messengers in mycobacteria.IMPORTANCEOur work has expanded the horizon of (p)ppGpp and c-di-GMP signaling in Gram-positive bacteria. We have come across a novel observation thatM. smegmatisneeds (p)ppGpp and c-di-GMP for cold tolerance. We had previously shown that the ΔrelMsmand ΔdcpAstrains are defective in biofilm formation. In this work, the overproduction of (p)ppGpp and c-di-GMP encasedM. smegmatisin a biofilm-like matrix, which shows that both (p)ppGpp and c-di-GMP are needed for biofilm formation. The regulation of cell length and cell division by (p)ppGpp was known in mycobacteria, but our work shows that c-di-GMP also affects the cell size and cell division in mycobacteria. This is perhaps the first report of c-di-GMP regulating cell division in mycobacteria.

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