BACTERIAL BIOFILM STATES ON THE GENETIC MAKEUP OF THE ORGANISM AND ITS ENVIRONMENT

1. Department of Biotechnology and Bioinformatics Centre Barkatullah University, Bhopal (M.P.). 2. Department of Pharmacy, Barkatullah University, Bhopal (M.P.). ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 20 August 2020 Final Accepted: 24 September 2020 Published: October 2020

The intent of this review is to consider the reasons why bacteria switch from a free-floating to a biofilm mode of growth. The currently available wealth of data pertaining to the molecular genetics of biofilm formation in commonly studied, clinically relevant, single-species biofilms will be discussed in an effort to decipher the motivation behind the transition from Planktonic to sessile growth in the human body. Four potential incentives behind the formation of biofilms by bacteria during infection are considered; protection from harmful conditions in the host (defense); sequestration to a nutrient-rich area (colonization); utilization of cooperative benefits (community); biofilms normally grow as biofilms and Planktonic cultures are an in vitro artifact (biofilms as the default mode of growth).

…………………………………………………………………………………………………….... Introduction:-
The genuine and unavoidable clinical effect of bacterial biofilms has motivated numerous analysts to research the administrative instruments behind their arrangement and disintegration, with a definitive objective of pinpointing explicit focuses for chemotherapeutic operators. Various target quality coordinated and in addition worldwide proteomics-and genomics-based investigations have led to the distinguishing proof of a plenty of qualities related with biofilm advancement. Dealing with the jobs of these qualities is in any case, an exceedingly intricate assignment. For a certain something, the administrative procedures of biofilm elaboration are patterned and dynamic. At the end of the day, outside conditions trigger changes in the outflow of a subset of qualities required for biofilm arrangement. The development of a biofilm thus adjusts the microenvironment of its own occupants which at that point prompts extra changes in quality articulation and further development of the biofilm, etc. Confusing the investigation of quality articulation in biofilms significantly further, biofilm occupants are heterogeneous. Malady related biofilms can be multi-species or even multi-kingdom, for example, the biofilms associated with tooth rot, or single-species, for example, those engaged with endocarditic, yet even microbes inside single-species biofilms are heterogeneous as for quality articulation. This is because of dispersion constraints conferred by the biofilm, which result in nearby varieties in pH, supplement and oxygen accessibility, and groupings of bacterial metabolites. Over these complexities, biofilm examines are perplexed by the inborn confinements of the in vitro biofilm models and the procedures accessible to think about the jobs of these qualities. Regardless of the difficulties related with the investigation of biofilms, similar and exhaustive examination of the majority of the current information can empower one to illustrate congruencies and along these lines, internationally huge facts end up divulged.

Microscopic organisms shape biofilms:
As per Darwin's hypothesis of development, the main genuine main thrust behind the strategy of any life form is regenerative wellness. Any activity that builds multiplication will persist inside animal varieties. In this manner, when we talk about the main impetus behind biofilm arrangement, we are making the inquiry "How does the biofilm method of development advance survival and proliferation of the phone?" It nearly appears to be illogical that the biofilm method of development could give a regenerative wellness advantage when one thinks about that biofilm microorganisms have a diminished rate of development in respect to microscopic organisms developing planktonically in soup culture. Outside of the research facility, be that as it may, microorganisms once in a while, if at any point, end up in a situation as supplement rich as culture media, and in these not exactly perfect conditions, there are various wellness preferences bestowed by the biofilm method of development. The more we find out about the hereditary control of biofilm arrangement, the more we comprehend about the general jobs of these advantages and about the powers that drive the change to the biofilm method of development. Biofilms are impervious to physical powers, for example, the shear powers delivered by blood stream and the washing activity of spit. Living beings inside biofilms can withstand supplement hardship, pH changes, oxygen radicals, disinfectants, and anti-infection agents superior to Planktonic creatures. Biofilms are additionally impervious to phagocytosis, and the phagocytes that endeavor an attack on the biofilm may really accomplish more damage to encompassing tissues than to the biofilm itself. The ceaseless idea of specific diseases is inarguably because of the advancement of a versatile biofilm. The insusceptibility of biofilms isn't totally seen yet is likely needy upon various biofilm-explicit attributes including moderate development and physiologic heterogeneity of the occupants. Another essential attribute that braces biofilm opposition is the sticky lattice which may contain DNA and different polymers however all in all, is transcendently made out of exopolysaccharides.
The critical job of exopolysaccharide (EPS) in both the early and late phases of biofilm arrangement is exemplified by the obvious nearness of qualities associated with polysaccharide union in Tables 1 In Escherichia coli, csgA, which encodes a protein associated with thecombination of colonic corrosive, is engaged with accumulation and algC, the quality required for alginate amalgamation assumes a job in Pseudomonas aeruginosa biofilms [4][5][6]. EPS union is critical in the advancement of gram-positive biofilms also. Glucan restricting protein GbpA is a glucosyltransferase that has been embroiled in sucrose-subordinate polysaccharide generation and biofilm arrangement in S. mutans [7]. What's more, the intercellular adhesin locus (icaADBC) in Staphylococcus aureus and Staphylococcus epidermidis encodes the quality items in charge of the amalgamation of a β-1-6-connected poly-Nacetylglucosamine polymer called PNAG or PIA (polysaccharide intercellular adhesin) [8]. A feeble PNAGdelivering strain holds the basic morphology of a youthful biofilm while a solid PNAG-creating strain shapes tight mushroom-like micro colonies isolated by wide channels. Notwithstanding its jobs in accumulation and biofilm structure, EPS has an impact in protection, empowering biofilms to oppose shear powers and phagocytosis by provocative cells [2]. Some proof recommends that EPS may likewise be associated with resilience of biofilms to antimicrobial specialists however this is as yet a matter of discussion [3]. In any case, if the sole power driving EPS generation and biofilm development is protection from threats experienced in the body, at that point what are the natural signals that caution microscopic organisms that they have to reinforce their guards? Certain bacterial species may have advanced to switch on translation of qualities required for EPS amalgamation in light of certain natural improvements that are experienced upon host passage, before the safe framework mounts an explicit assault [9]. For instance, certain upgrades that reflect the physiology of the human body, for example, press hardship and osmotic pressure, incite the statement of qualities encoding proteins that blend EPS in staphylococci and enterococci [10,11].
Confocal minuscule imaging exhibits the impact of exopolysaccharide elaboration on the structure of S. aureus biofilms. S. aureus clinical seclude strain MN8, and the isogenic, constitutive PNAG over-creating subsidiary strain MN8m were permitted to frame biofilms on collagen-covered glass coverslips for 48 h sub-current conditions. The biofilms were recolored utilizing the Bac Light Live/Dead pack which recolors live microbes green and dead microorganisms red. These confocal pictures show that the dimension of PNAG blend assumes a basic job in biofilm structure. MN8 framed a to some degree unstructured biofilm, while the PNAG-overproducing strain MN8m shaped a profoundly organized biofilm with thick mushroom-formed micro colonies isolated by extensive channels. The association of stress reaction controllers in biofilm arrangement would bolster the speculation that the inspiration driving biofilm development is barrier, yet the commitment of these controllers is to some degree hazy. As showed in Table 1, examines have embroiled the pressure reaction controllers Dgk, σB, and RpoS, of S. mutans, S. aureus, and E. coli (individually) in biofilm development [12][13][14][15]. Different examinations be that as it may, question the jobs of σB and RpoS in biofilm development [16][17][18]. In P. aeruginosaRpoS articulation is down in biofilms however articulation of RpoH, a sigma factor that has been connected to the stationary stage and stress, is lifted [19]. The job of the pressure reaction controllers may rely on the conditions under which biofilm development is activated or upon the hereditary foundation of the bacterial cell, again proposing that what we sort as a biofilm really speaks to a gathering of various development states. Biofilms are inarguably strong, yet in the event that guard is the significant main thrust behind the bacterial method of development in the human body, at that point for what reason would the microorganisms shape a sessile network in such a cold place? In whole, it is obvious that the pressure isn't the main trigger for this method of development.

Colonization: biofilm development as an instrument to stay in a positive specialty
People and different creatures have created multifaceted insusceptible frameworks for one basic reason: microorganisms are ceaselessly endeavoring to occupy their bodies. The body, or possibly parts of it, is supplement rich and generally stable regarding water content, oxygen accessibility, and temperature. Therefore, there is a ceaseless race between the advancement of the host safe framework and the movement of bacterial procedures to sidestep it. Now and again, a bargain has been made, and accordingly, the body is occupied by countless, a significant number of which exist as biofilms. As the body is clearly an engaging spot for microbes to live, it might be that the essential inspiration for changing to the biofilm method of development is to stay settled.
Microorganisms have various methodologies to guarantee that they stay settled in the human body. Bacterial surface proteins that predicament to have extracellular framework proteins, for example, fibronectin, fibrinogen, vitronectin, and elastin are alluded to as MSCRAMMs (microbial surface part perceiving cement grid atoms) and frequently assume a key job in beginning adherence of microscopic organisms to strong surfaces inside the host [20]. S. aureus is especially remarkable for the wealth of MSCRAMMs that it can create, including clustering factors an and B (ClfA/B), fibronectin restricting elements An and B (FnBA/B), and a collagen restricting protein (Cna). S. epidermidis delivers no less than two autolysin-adhesins that dilemma to fibronectin and the fibrinogen restricting protein Fbe [8]. Streptococcus pyogenes contains qualities for fibronectin (prtF) and fibrinogen (emm) restricting proteins [20]. The oral streptococci have developed to tie to the pellicle or molding film on tooth surfaces which is made out of salivary glycoproteins and lipids. The salivary agglutinin glycoprotein restricting proteins (SspA and SspB in Streptococcus gordonii and SpaP in S. mutans), and salivary amylase restricting proteins of different oral streptococci help in official to the pellicle on the surface of teeth [7,21]. Flagella, pili, and fimbriae have additionally been involved in adherence of Vibrio cholerae, E. coli, P. aeruginosa, and Salmonella enterica [22]. Strikingly, this recommends the primary job of adhesins, pili, and flagella is in introductory connection, and that once the improvement of the biofilm has passed this stage, the proteins are never again required and their appearance is hindered. By and large, microscopic organisms deliver a noteworthy exhibit of adhesins that seem to have advanced as a way to occupy the human body.
Additionally, in help of the theory that biofilm development is a component for life forms to remain put in the ideal condition of the human host, is the finding that carbon catabolism actuated quality control assumes a basic job in biofilm arrangement (Table 1). Exopolysaccharides articulation and biofilm elaboration are extraordinarily improved in specific microscopic organisms, including the pseudomonads, V. cholerae, and E. coli, the staphylococci and the streptococci, when glucose or another promptly utilizable carbon source is inexhaustible [4,[23][24][25]. At the point when supplement sources are exhausted, the microscopic organisms disengage and end up planktonic, recommending that supplement hardship is a trigger to proceed onward, looking for a superior territory. Glucose-initiated exopolysaccharide generation might be multi-useful. It is conceivable that glucose basically fills in as a substrate in the EPS amalgamation pathway however considers with S. aureus in our lab propose that, at any rate for this living being, this isn't the situation. Glucose seems to increase EPS elaboration at the dimension of transcriptional direction as opposed to at the dimension of EPS amalgamation [25]. A second plausibility, which underpins the biofilm as a method of safeguard is that microscopic organisms may have advanced to translate hoisted glucose levels as a signal that it is in the circulatory system, and that it needs to frame a biofilm to expel itself from flow and shield itself from the resistant framework. On the other hand, polysaccharide generation may work as a system of glucose stockpiling amid times of bounty, and additionally as a component to increase the amassing stage with the goal that when the living being ends up in a situation wealthy in supplements it can possess 607 that specialty. With the majority of the unpredictable instruments that pathogenic and commensally microscopic organisms have advanced to get by in the human body, unmistakably the advantages that we manage the cost of them exceed the obstacles conferred by our resistant frameworks.

Community: biofilms and mutual conduct Are biofilms multicellular living beings:
One such speculation is that biofilms ought to be viewed as multicellular life forms and that biofilm microorganisms display helpful, unselfish conduct [26]. The conduct of microscopic organisms inside biofilms has even started wariness about the Darwinian hypotheses of development [27]. Speculative difficulties to very much acknowledge hypotheses are engaging yet without logical proof to back them up they remain simply philosophical, and there has not yet been a push to experimentally approve the test to our present thoughts regarding development. As of late in any case, numerical demonstrating of biofilm frameworks and logical trials are being intended to test whether agreeable, philanthropic conduct in microorganisms is perfect with the standard hypothesis of advancement [28].
There are undoubtedly similitudes between biofilm microscopic organisms and multicellular creatures. For example, microorganisms (counting planktonic microbes) can detect their environment, and this empowers them to alter their metabolic procedures to amplify the utilization of accessible substrates and to shield themselves from inconvenient conditions. At the point when microorganisms are developing inside a biofilm, these adjustments in quality articulation result in phenotypic heterogeneity inside the biofilm which can be deciphered as specialization or division of work like cell separation seen in multicellular living beings. Furthermore, microbes discharge substances alluded to as auto inducing signals, which impact quality articulation and might be a method by which cells speak with each other. There is even a developing group of proof that microscopic organisms show charitable conduct and can experience a procedure like modified cell demise, again suggestive of multicellularity [29]. Nonetheless, there are basic refinements among microbes and multicellular creatures. For instance, while bacterial cells can respond and adjust to their ecological environment, they don't for all time separate. For example, one can separate colonic epithelial cells from a human and develop them in tissue culture medium, and despite the fact that the cells are abruptly looked with radical changes in their encompassing milieu, they keep on developing as colonic epithelial cells and can even frame an energized monolayer like colonic epithelium. Researchers have given much exertion to creating strategies to "undifferentiated" separated cells, yet the procedure of cell separation, even in straightforward multicellular life forms, isn't actually turned around by any common means. This is on the grounds that their hereditary administrative examples have been for all time adjusted. Assuming be that as it may, you expel bacterial cells from a biofilm and profoundly change their ecological conditions then they will rapidly adjust to their new natural environment and show phenotypic changes. Contingent upon the conditions in which they are developed, they will even change over back to the planktonic method of development. Bacterial cells don't separate; rather they react to their ecological surroundings by adjusting their quality articulation to suit their very own requirements for survival. Hence, it is progressively exact to allude to biofilms as intuitive networks instead of contrasting them with multicellular creatures. In any case, the network way of life is likely an imperative inspiration for biofilm development and furnishes its individuals with various advantages. Notwithstanding the upside of protection from ecological changes, which is examined in the guard area, the biofilm may profit by various properties of a public presence including division of the metabolic weight, quality exchange, and sacrificial conduct.

Division of the metabolic weight:
Dispersion confinements bestowed by the biofilm structure result in neighborhood varieties in supplement accessibility, pH, and oxygen strain. In this manner, the microorganisms inside biofilms are definitely heterogeneous as for quality articulation. Numerous biofilms are comprised of an assortment of bacterial animal varieties and some even contain blends of microscopic organisms and growths. The individuals from these blended biofilms have diverse necessities and perform distinctive metabolic capacities making commensalism a boundless wonder in biofilms [26]. For instance, while early colonizers of the oral depression are vigorous or facultative anaerobic, restricted oxygen dissemination through the biofilm gives an ecological specialty permitting to later colonization by commit anaerobes [7]. An examination in which advertiser action was checked as a component of the statement of a fluorophore showed that heterogeneity in the quality articulation profiles of the individual cells exists even inside single-species biofilms [30]. Almost certainly, this heterogeneity converts into specific elements of cells inside a biofilm [30]. Fruiting body development by Myxobacteria is regularly refered to for instance of cell specialization in microscopic organisms and it is an alluring thought that this marvel happens in other microbes too [26]. In spite of the fact that it has not been authoritatively demonstrated, the heterogeneity inside biofilms may undoubtedly result in a "division of work" of sorts and unquestionably expands the metabolic proficiency of the populace in general.

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A famous thought is that such division of work is coordinately controlled inside biofilms through intercellular correspondence. Auto inducing signals are little atoms, for the most part homoserine lactones in gram-negatives and peptides in gram-positives that are constitutively discharged by microorganisms and which, when present at a basic focus will prompt the statement of specific qualities. Auto inducing signals are as often as possible alluded to as majority detecting signals since when a bacterial populace achieves a sufficiently high thickness; the nearby focuses achieve edge levels and modify quality articulation. Nonetheless, it has not been indicated indisputably that microorganisms really react to the aggregation of a majority, and it has been proposed that the more naturally noteworthy job of the autoinducing signals is to transfer data to the bacterial cell about neighborhood dissemination rates [31]. One model utilized is the discharge of a protease which is required to debase exogenous proteins with the goal that the microorganisms can absorb amino acids. Under states of decreased dissemination or blending, emitted proteases and the proteins corrupted by them would stay in the region of, and advantage the cell. It is in this manner sensible that microscopic organisms would confine articulation of emitted proteins under states of high blending and dissemination. There are additionally instances of auto inducer impacts that don't promptly fit this model. The dissemination detecting model recommends that a bacterial cell reacts to its own discharged signs, however acknowledgment of and reaction to signals emitted by heterologous species has been all around recorded [32]. Almost certainly, both dissemination detecting and majority detecting are parts of auto inducing signals yet a progressively exact answer fusing jobs for both of these wonders anticipates further examination.
While the essential capacity of auto inducing signals stays hazy, their job in biofilm advancement is significantly increasingly uncertain. As is demonstrated in Table 1, one examination found a job for the LuxS framework in S. mutans however two extra examinations demonstrated that LuxS was not required for biofilm development [12,33,34]. Similarly jumbling outcomes were gotten when distinctive specialists contemplated the job of the lasRlasI majority detecting framework in P. aeruginosa [35]. Besides, there is proof that the frill quality controller (Agr) which is engaged with majority detecting in the staphylococci really restrains biofilm arrangement [36]. A later report recommends that the Agr impact is reliant upon the stream quality over the biofilm and that under static conditions, Agr diminishes biofilm arrangement, under low to direct stream it doesn't influence biofilm development, and under exceptionally solid stream it increments biofilm arrangement [30]. These outcomes may bolster the dispersion detecting hypothesis on the off chance that one thinks about that under fast stream, the autoinitiating signs may quickly diffuse out of the biofilm. A biofilm speaks to both a majority and gives confinements on dissemination, so paying little mind to whether one acknowledges the dispersion detecting or the majority detecting speculation, no doubt, at any rate externally, that auto-actuating signals impact its improvement. In parts of the human body notwithstanding, particularly in spots, for example, heart valves and teeth, biofilms are exposed to solid shear powers which may keep autoinducing signal dimensions low. An ongoing report demonstrates that in the human lung, the acyl-homoserine lactone majority detecting sign of P. aeruginosa is inactivated by some unidentified host cell-related factor [37]. Does this demonstrate the superfluity of majority detecting and imply that P. aeruginosa can set up a biofilm in the lung in spite of resistant interceded hindrance of majority detecting, or is the finding that the insusceptible framework focuses on this flag suggestive of its significance in biofilm arrangement? The appropriate response is hazy and the job of majority detecting in biofilm development stays tricky.

Gene exchange:
Nucleic corrosive is the reason for advancement and therefore its one genuine design is to recreate and propagate its own particular code. A regenerative wellness preferred standpoint will sustain the hereditary material of a person. Similar tenets apply to commit irresistible specialists, for example, infections and plasmids, and as these operators can not duplicate their very own hereditary material, they would stop to exist without a way to spread starting with one life form then onto the next. Bacteriophage and plasmids have in this manner both developed components to advance their upkeep inside a bacterium and their spread to other microscopic organisms. For instance, bacteriophage back off their explicative apparatus and coordinate into the bacterial chromosome with the goal that their genome is imitated as the cell isolates. Plasmid replication is a costly procedure for a bacterial cell and plasmids are rapidly lost except if there are required or gainful. Plasmids have in this manner advanced a somewhat intricate technique for survival. They convey toxin-neutralizing agent quality sets which make their upkeep important for bacterial survival [38]. The plasmid-encoded poison is a steady protein and the antibody is a labile protein. At the point when a bacterial cell separates the little girl cell acquires both poison and counteragent. On the off chance that the cell neglects to repeat the plasmid as it partitions or in the event that the little girl cell neglects to acquire the plasmid, the supply of labile neutralizing agent quickly decays though the poison waits and wrecks the without plasmid little girl cell.

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These craftiness support strategies guarantee vertical exchange of phages and plasmids however so as to be fruitful, a phage or irresistible plasmid should likewise use flat exchange. A biofilm is the perfect condition for even trade of hereditary material [39]. The closeness encourages fast spread of phage and additionally conjugation and take-up of plasmid DNA by able microbes. Plasmids and phage have thusly created strategies to incite the progress to the biofilm method of development in their host so they can spread to uninfected microscopic organisms and some of the time even to cross the species boundary [40]. The pili encoded in various conjugative plasmids hold fast nonspecifically to strong surfaces and to other microorganisms prompting a sensational increment in biofilm development of E. coliand other Gram-negative microbes [41]. By prompting the change to the biofilm method of development, the plasmid is likely expanding its odds for flat transmission. Also, various phage qualities, including phage coat protein qualities, are initiated in P. aeruginosa biofilms, supporting that a powerful system for even phage transmission is to reemerge the irresistible cycle amid the biofilm method of development [19]. Essentially, we may need to think about that biofilm development benefits bacterial wellness as well as the proliferative capability of bacteriophage and plasmids also. Level quality exchange inside biofilms may likewise straightforwardly advantage the microorganisms through the trading of anti-infection obstruction determinants. In S. gordonii, the statement of capability factors has been involved as both a reason and an impact of biofilm development supporting a job for trade of hereditary material in biofilms [39,42]. Regardless of whether the essential capacity of ability factors is to acclimatize outer DNA as a way to expand their hereditary decent variety or basically to utilize it as a supplement source is dubious, yet the final product is that the biofilm is a perfect situation for the trading of hereditary material. The inspiration of microscopic organisms themselves and in addition plasmids and bacteriophage to trade hereditary material may all assume a critical job during the time spent biofilm advancement.

The biofilm as the default mode of growth:
In the laboratory, bacteria are generally grown planktonically, but the utopian microcosms created in culture vessels are designed to maximize bacterial growth rates, not to replicate natural growth conditions of the bacteria. In fact, some bacterial species appear to constitutively utilize the biofilm mode outside of the lab. The oral streptococci are very highly adapted to sessile growth on the surface of teeth. Most of the oral bacterial species lack an environmental niche and are found almost exclusively within the mouth [24]. For these bacteria, planktonic growth would cause them to be quickly washed away by saliva, swallowed and destroyed within the acidic juices of the stomach. These bacteria likely spend the majority of their natural existence growing as a biofilm.
It is possible that the presence of a suitable substrate for attachment is all that is required to trigger biofilm formation. There is mounting evidence that immediately subsequent to the initial adherence of bacterial to a solid surface, changes in gene regulation begin to occur [4,44]. This suggests that cells actually sense the solid surface to which they are attached and that this sensing system triggers a signaling cascade that may lead to some of the early gene expression patterns necessary for biofilm formation. For example, in P. aeruginosa, expression of algC, a gene required for alginate synthesis, is increased within minutes of attachment, and when S. epidermidis makes contact with a solid surface, the normally spherical cell forms a leg-like appendage [45,46]. These findings suggest that, similar to eukaryotic cells, bacterial cells possess surface-sensing systems that induce intracellular signals powerful enough to result in transcriptional and morphologic changes.
The sensing mechanisms utilized by bacteria to detect adherence are not well understood. Changes in the perceived osmolarity caused by charges on solid surfaces may be an important cue for bacteria to recognize surfaces [22]. The EnvZ-OmpR two-component system which is involved in sensing environmental osmolarity, has also been shown to regulate expression of curli and colanic acid [47,48]. The fibrillar surface structure curli plays a role in adherence and colanic acid is an exopolysaccharide involved in aggregation. The role of osmolarity in biofilm regulation has also been noted in staphylococci [13] and Pseudomonas fluorescens [49]. Overall, the biofilm mode of growth may be the default mode of growth for at least some bacterial species suggesting that we should be questioning what triggers the planktonic mode of growth rather than what motivates the biofilm mode of growth.

Conclusions:-
Scientific interest in biofilms has exploded in the past decade. This fascination with biofilms is due in large part to their presumed clinical relevance. But it is also, undeniably, due to the appeal of projecting traits of higher organisms on these life forms that were once thought to be so simple and autonomous. The ability of prokaryotes to adapt to their surroundings is indeed remarkable, but whether they actually communicate, coordinate, and specialize within biofilms for the benefit of the community, as opposed to simply reacting to their environments in order to 610 selfishly promote their own survival, has not yet been sufficiently established. Unfortunately, often make the erroneous conclusion that certain questions are purely philosophical and cannot be tested scientifically. In fact, such questions can often, if not always, be objectively examined, and scientists have recently begun to develop mathematical models that predict the relative impacts of altruistic vs. selfish behavior on the survival and propagation of bacteria [28]. In conclusion, it is evident that bacteria reap a number of benefits from the biofilm mode of growth and it is likely that different forces motivate bacteria to transition to one of a variety of biofilm states depending on the genetic makeup of the organism and its environment. The alternative motives for biofilm formation presented in this review are by no means exhaustive or mutually exclusive and because it is such a complex process, they may all have a role.