*5.4.1 Human health and pathogenicity*

A wide spectrum of pathogenic microorganisms exists and some form biofilms with microplastics in aquatic environments [111]. Freshwater ecosystem analysis has the formation of biofilms on microplastic substrates by a selected grouping of human pathogens utilizing high-throughput sequencing of 16S rRNA that had distinctive community structures [112]. Opportunistic human pathogens such as *Pseudomonas monteillii*, *Pseudomonas mendocina*, and a plant pathogen *Pseudomonas syringae* were detected forming a microplastic biofilm. The opportunistic pathogens were enriched in a biofilm, and the microplastic biofilm exhibited a unique microbial community structure. Distinctive antibiotic resistance genes were detected in the microplastic biofilm. It appears that microplastic surfaces are novel microbial niches and may serve as a vector for antibiotic resistance genetic traits and pathogens in freshwater bodies, engendering environmental risk and exerting adverse impacts on human health [113].

*Vibrios* are Gram-negative-curved bacilli naturally occuring in marine, estuarine, and freshwater systems [114]. A group of factors has been shown to drive certain microorganisms' virulence in *in vivo* studies, and some are fitness factors in the environment [115]. Factors associated with virulence, nutrient acquisition, competition, survival in unfavorable biotic and abiotic conditions, and attachment and colonization were found to be in the group [116]. As human and animal pathogens, it is important to understand virulence factors, attachment factors, regulatory factors, and antimicrobial resistance factors, which have been characterized for their importance to the organism's fitness apart from its external environment. Virulence and fitness factors were designated and characterized for the three main human pathogens *Vibrio cholerae*, *V. parahaemolyticus*, and *Vibrio vulnificus*.

Bacterial fitness depends on the ability to colonize and grow in hosts, avoid immunological inhibition, and be transmitted to a new host [117]. Established virulence factors can be considered fitness factors, as these factors render the organisms more fit under specific circumstances. Mobile components such as pathogenicity islands carry genes that strengthen the fitness of *Vibrios* even when not producing a toxic effect in a host [118]. Elevated mutation rates can also facilitate evolution of bacteria, making it possible to survive under a wide array of environmental conditions [119].

The three-dimensional complex communities of microbes found in biofilms form on both organic and inorganic substrates that render bacteria more protected from environmental stressors [112]. Biofilms have been demonstrated and characterized for *V. vulnificus*, *V. parahaemolyticus*, *V. cholerae*, *V. fischeri*, *V. harveyi*, and *V. anguillarum* [120].

Pathogen fitness factors and virulence factors produce similar effects in different environments [121]. In unfavorable environments, microbial survival requires factors supporting attachment and colonization such as polysaccharide synthesis, secretion, colonization, motility, toxicity, and genetic regulation. Accompanying these factors may be additive and synergistic effects important to active colonization of biotic and abiotic substrates.

### **6. Conclusions**

The global society's concern over microplastics is directly related to its persistence and potential adverse effects on aquatic biota. In aquatic environments, microorganisms can colonize surfaces by forming adherent biofilms. Biofilm's role in the fate and effects of microplastic has not been completely delineated since active research is aimed to fill copious information gaps. The physical interactions of plastic surfaces and their microbial colonizers is becoming more functionally integrated in the understanding of the effects of microplastic weathering, vertical transport in the water column, and processes of sorption and contaminant release [122]. Biofilmplastic interactions are recognized for their influence on the fate and effects of microplastics through modification of a particle's physical and chemical properties.

The use of proper and clear terminology for the design of data collection and supporting analytical protocols is necessary for the collection of representative data which is important to the strategic design of research directions based on consensus data development [42]. The necessary analytical determinations (biological, chemical, and physical) developed from a wide array of current and developing technologies offer answers to questions concerning the details of microplastics in the environment. Spatial information, contamination sources, fate, and environmental concentrations are necessary to a timely and proficient gathering of information [48]. New and novel analytical methodology designed to assist the chemical, biological, and physical characterization of samples is welcomed [50].

**315**

*The Importance of Biofilms to the Fate and Effects of Microplastics*

require the use of environmentally representative biofilm.

An understanding of surface biofouling of submerged surfaces is important to decipher surface colonization processes relative to of the behavior of plastic in the environment [123–126]. An enhanced understanding of biofilm formation on submerged surfaces is required to develop a more complete pictures of microbial colonization and the basic processes involved in biofilm formations. Biofilm-plastic interactions important to hydrodynamic processes, such as vertical transport,

The effect of biofilm formation and its connection to the kinetics of chemical partitioning required additional scrutiny [127, 128]. The complexity of surfaces available to sorption processes needs attention to discover the relative importance of the multiple surface adsorption of organic and inorganic pollutant chemicals. The importance of surface topography to the sorption process requires further research. Mechanisms to explain toxic chemical transport by microplastics employing established biofilm contaminated with heavy metals and organic chemicals will be very helpful.

Microbial effects specific to the ability of biofilm-forming microorganisms on a microplastic surface in contact with aqueous media are important to the development of biofilms and their control. Human pathogens such as strains of *Vibrio* spp. have been isolated in formed biofilm on microplastics. The pathogen-populated biofilms must be scrutinized for their possible role in the transmission of materials

Studies are available suggesting that biofilms on microplastics do not present a threat over biofilms on naturally occurring surfaces [130, 131]. The pathogenic populated biofilms are viewed as having no new adverse effect on human food supplies. Since we are still an early state of learning with the environmental effects of microplastics, it is incumbent that we continue to scrutinize biofilm effects and

This chapter has focused on the question of a role for bacterial biofilms to the environmental effects attributable to microplastics. The importance of biofilms to plastics and their degradation is becoming more completely revealed through continuing focused research effort. The alacrity with which biofilms form on plastic in the environment is functionally connected to ambient conditions and the weather effects to which the plastic has been subjected. Microplastics and adherent biofilms provide potential vector mechanisms to assist the transport of pollutant chemicals

The findings and conclusions in this chapter have not been formally disseminated by the United States Environmental Protection Agency and should not be

their relation to human health and the health of aquatic ecosystems [132].

and pathogens to a wide area of the aquatic environment.

construed to represent any agency determination or policy.

No conflict of interest is known or expected.

*DOI: http://dx.doi.org/10.5772/intechopen.92816*

that could be lethal [129].

**Conflict of interest**

**Disclaimer**

### *The Importance of Biofilms to the Fate and Effects of Microplastics DOI: http://dx.doi.org/10.5772/intechopen.92816*

*Bacterial Biofilms*

*anguillarum* [120].

**6. Conclusions**

tion of biotic and abiotic substrates.

*Vibrios* are Gram-negative-curved bacilli naturally occuring in marine, estuarine, and freshwater systems [114]. A group of factors has been shown to drive certain microorganisms' virulence in *in vivo* studies, and some are fitness factors in the environment [115]. Factors associated with virulence, nutrient acquisition, competition, survival in unfavorable biotic and abiotic conditions, and attachment and colonization were found to be in the group [116]. As human and animal pathogens, it is important to understand virulence factors, attachment factors, regulatory factors, and antimicrobial resistance factors, which have been characterized for their importance to the organism's fitness apart from its external environment. Virulence and fitness factors were designated and characterized for the three main human pathogens *Vibrio cholerae*, *V. parahaemolyticus*, and *Vibrio vulnificus*.

Bacterial fitness depends on the ability to colonize and grow in hosts, avoid immunological inhibition, and be transmitted to a new host [117]. Established virulence factors can be considered fitness factors, as these factors render the organisms more fit under specific circumstances. Mobile components such as pathogenicity islands carry genes that strengthen the fitness of *Vibrios* even when not producing a toxic effect in a host [118]. Elevated mutation rates can also facilitate evolution of bacteria, making it possible to survive under a wide array of environmental conditions [119]. The three-dimensional complex communities of microbes found in biofilms form on both organic and inorganic substrates that render bacteria more protected from environmental stressors [112]. Biofilms have been demonstrated and characterized for *V. vulnificus*, *V. parahaemolyticus*, *V. cholerae*, *V. fischeri*, *V. harveyi*, and *V.* 

Pathogen fitness factors and virulence factors produce similar effects in different environments [121]. In unfavorable environments, microbial survival requires factors supporting attachment and colonization such as polysaccharide synthesis, secretion, colonization, motility, toxicity, and genetic regulation. Accompanying these factors may be additive and synergistic effects important to active coloniza-

The global society's concern over microplastics is directly related to its persistence and potential adverse effects on aquatic biota. In aquatic environments, microorganisms can colonize surfaces by forming adherent biofilms. Biofilm's role in the fate and effects of microplastic has not been completely delineated since active research is aimed to fill copious information gaps. The physical interactions of plastic surfaces and their microbial colonizers is becoming more functionally integrated in the understanding of the effects of microplastic weathering, vertical transport in the water column, and processes of sorption and contaminant release [122]. Biofilmplastic interactions are recognized for their influence on the fate and effects of microplastics through modification of a particle's physical and chemical properties. The use of proper and clear terminology for the design of data collection and supporting analytical protocols is necessary for the collection of representative data which is important to the strategic design of research directions based on consensus data development [42]. The necessary analytical determinations (biological, chemical, and physical) developed from a wide array of current and developing technologies offer answers to questions concerning the details of microplastics in the environment. Spatial information, contamination sources, fate, and environmental concentrations are necessary to a timely and proficient gathering of information [48]. New and novel analytical methodology designed to assist the chemical, biological, and physical characterization of samples is welcomed [50].

**314**

An understanding of surface biofouling of submerged surfaces is important to decipher surface colonization processes relative to of the behavior of plastic in the environment [123–126]. An enhanced understanding of biofilm formation on submerged surfaces is required to develop a more complete pictures of microbial colonization and the basic processes involved in biofilm formations. Biofilm-plastic interactions important to hydrodynamic processes, such as vertical transport, require the use of environmentally representative biofilm.

The effect of biofilm formation and its connection to the kinetics of chemical partitioning required additional scrutiny [127, 128]. The complexity of surfaces available to sorption processes needs attention to discover the relative importance of the multiple surface adsorption of organic and inorganic pollutant chemicals. The importance of surface topography to the sorption process requires further research. Mechanisms to explain toxic chemical transport by microplastics employing established biofilm contaminated with heavy metals and organic chemicals will be very helpful.

Microbial effects specific to the ability of biofilm-forming microorganisms on a microplastic surface in contact with aqueous media are important to the development of biofilms and their control. Human pathogens such as strains of *Vibrio* spp. have been isolated in formed biofilm on microplastics. The pathogen-populated biofilms must be scrutinized for their possible role in the transmission of materials that could be lethal [129].

Studies are available suggesting that biofilms on microplastics do not present a threat over biofilms on naturally occurring surfaces [130, 131]. The pathogenic populated biofilms are viewed as having no new adverse effect on human food supplies. Since we are still an early state of learning with the environmental effects of microplastics, it is incumbent that we continue to scrutinize biofilm effects and their relation to human health and the health of aquatic ecosystems [132].

This chapter has focused on the question of a role for bacterial biofilms to the environmental effects attributable to microplastics. The importance of biofilms to plastics and their degradation is becoming more completely revealed through continuing focused research effort. The alacrity with which biofilms form on plastic in the environment is functionally connected to ambient conditions and the weather effects to which the plastic has been subjected. Microplastics and adherent biofilms provide potential vector mechanisms to assist the transport of pollutant chemicals and pathogens to a wide area of the aquatic environment.
