Usage

1. Input Files

2. Quick Start

3. Options

4. Basic Parameters

5. Cleaning Functions

6. Visualisation Functions

7. Interpretation functions

8. Editing functions

CIAlign is used to process multiple sequence alignments (MSAs) - sets of nucleotide or amino acid sequences which have already been aligned with an external tool.

Input Files

The input for CIAlign is an aligned MSA in FASTA format.

Quick Start

CIAlign --infile INFILE --outfile_stem STEM OPTIONS

Where INFILE is the FASTA file you would like to process, STEM is a prefix for the output files and OPTIONS lists the functions you would like to run and the parameters you would like to use.

For example, to run the remove insertions function, with default settings, on the file example1.fasta and generate ri_clean.fasta.

CIAlign --infile example1.fasta --outfile_stem ri --remove_insertions

To run all functions with the default settings (please use this option cautiously):

CIAlign --infile example1.fasta --all

Specifying Options

Parameters can be specified in the command line OPTIONS or in a config file.

A template config file is provided in CIAlign/templates/ini_template.ini - edit this file and provide the path to the --inifile argument.

CIAlign --infile INFILE --outfile_stem STEM --inifile my_inifile.ini

If this argument is not provided command line arguments and defaults will be used.

Parameters passed in the command line will take precedence over config file parameters, which take precedence over defaults.

Command help can be accessed by typing CIAlign --help

Basic Parameters

Parameter	Description	Default
--infile	Path to input alignment file in FASTA format	None
--inifile	Path to config file	None
--outfile_stem	Prefix for output files, including the path to the output directory	CIAlign
--all	Use all available cleaning, visualisation and interpretation functions with default parameters	False
--clean	Use all available cleaning functions with default parameters	False
--visualise	Use all available mini alignment visualisation functions with default parameters	False
--interpret	Use all available interpretation functions with default parameters	False
--silent	Do not print progress to the screen	False
--help	Show all available parameters with an explanation	None
--version	Show the version	None

Beside these main parameters, the use of every function and corresponding thresholds can be specified by the user by adding parameters to the command line or by setting them in the configuration file. Available functions and their parameters are specified below.

CIAlign always produces a log file, specifying which functions have been run with witch parameters and what has been removed. It also outputs a machine parsable file that only specifies what has been removed with the original column positions and the sequence names.

Output files:

• OUTFILE_STEM_log.txt - general log file

• OUTFILE_STEM_removed.txt - removed columns positions and sequence names text file

Cleaning Functions

The CIAlign cleaning functions are designed to address several common issues with multiple sequence alignments, affecting the speed, complexity and reliability of specific downstream analyses.

All of these functions remove columns or rows from the alignment to address sources of noise.

• Remove divergent

• Remove insertions

• Crop ends

• Remove short

• Remove gap only

• Crop divergent

Each of these steps (if specified) will be performed sequentially in the order specified in the table below.

remove_divergent, remove_insertions, crop_ends and crop divergent require three or more sequences in the alignment, remove_short and remove_gap_only require two or more sequences.

Output files:

The “cleaned” alignment after all steps have been performed will be saved as OUTFILE_STEM_cleaned.fasta

The retain functions allow the user to specify sequences to keep regardless of the CIAlign results.

Remove Divergent

Removes divergent (outlier) sequences from the alignment. It is very common for an MSA to include one or a few outlier sequences which do not align well with the majority of the alignment. For some applications it is useful to remove these.

The remove divergent function specifically removes sequences with <= remove_divergent_minperc positions at which the most common residue in the alignment is present.

Parameter	Description	Default Value	Min	Max
--remove_divergent	Remove sequences with <= remove_divergent_minperc positions at which the most common base / amino acid in the alignment is present	False	NA	NA
--remove_divergent_minperc	Minimum proportion of positions which should be identical to the most common base / amino acid in order to be preserved	remove_divergent_minperc_def	remove_divergent_minperc_min	remove_divergent_minperc_max
--remove_divergent_retain	Do not remove sequences with this name when running the remove divergent function	None	NA	NA
--remove_divergent_retain_str	Do not remove sequences with names containing this character string when running the remove divergent function	None	NA	NA
--remove_divergent_retain_list	Do not remove sequences with names listed in this file when running the remove divergent function	None	NA	NA

Remove Insertions

Removes insertions which are not present in the majority of sequences (or regions which are deleted in the majority of sequences). Insertions or other stretches of sequence which are only present in a minority of sequences can lead to large gaps, these are sometimes of interest but can also complicate downstream analysis.

The remove insertions function removes regions from the alignment which are found in <= insertion_min_perc of the sequences but are surrounded by >= insertion_min_flank columns of higher coverage.

Parameter	Description	Default Value	Min	Max
--remove_insertions	Remove insertions found in <= insertion_min_perc of sequences from the alignment	False	NA	NA
--insertion_min_size	Only remove insertions >= this number of residues	insertion_min_size_def	insertion_min_size_min	insertion_min_size_max
--insertion_max_size	Only remove insertions <= this number of residues	insertion_max_size_def	insertion_max_size_min	insertion_max_size_max
--insertion_min_flank	Minimum number of bases on either side of an insertion to classify it as an insertion	insertion_min_flank_def	insertion_min_flank_min	insertion_min_flank_max
--insertion_min_perc	Remove insertions which are present in less than this proportion of sequences	insertion_min_perc_def	insertion_min_perc_min	insertion_min_perc_max

Crop Ends

It is common for an MSA to contain more gaps towards either end than in the body of the alignment, due to (for example) increased sequencing error towards the ends of reads, lower read coverage or assembly issues.

The crop ends function crops the ends of individual sequences if they contain a high proportion of gaps relative to the rest of the alignment. The number of gap positions separating every two consecutive non-gap positions at either end of the sequence is compared to a threshold (calculated from the total sequence length using crop_ends_mingap_perc) and if that difference is higher than the threshold, the start of the sequence will be reset to that position.

Parameter	Description	Default Value	Min	Max
--crop_ends	Crop the ends of sequences if they are poorly aligned	False	NA	NA
--crop_ends_mingap_perc	Minimum proportion of the sequence length (excluding gaps) that is the threshold for change in gap numbers.	crop_ends_mingap_perc_def	crop_ends_mingap_perc_min	crop_ends_mingap_perc_max
--crop_ends_redefine_perc	Proportion of the sequence length (excluding gaps) that is being checked for change in gap numbers to redefine start/end.	crop_ends_redefine_perc_def	crop_ends_redefine_perc_min	crop_ends_redefine_perc_max
--crop_ends_retain	Do not crop sequences with this name when running the crop ends function	None	NA	NA
--crop_ends_retain_str	Do not crop sequences with names containing this character string when running the crop ends function	None	NA	NA
--crop_ends_retain_list	Do not crop sequences with names listed in this file when running the crop ends function	None	NA	NA

Note: if the sequences are short (e.g. < 100), a low crop_ends_mingap_perc (e.g. 0.01) will result in a change of gap numbers that is too low (e.g. 0). If this happens, the change in gap numbers will be set to 2 and a warning will be printed.

Remove Short

Removes short sequences below a threshold length.

Parameter	Description	Default Value	Min	Max
--remove_short	Remove sequences <= remove_min_length amino acids from the alignment	False	NA	NA
--remove_min_length	Sequences are removed if they are shorter than this minimum length, excluding gaps.	remove_min_length_def	remove_min_length_min	remove_min_length_max
--remove_short_retain	Do not remove sequences with this name when running the remove short function	None	NA	NA
--remove_short_retain_str	Do not remove sequences with names containing this character string when running the remove short function	None	NA	NA
--remove_short_retain_list	Do not remove sequences with names listed in this file when running the remove short function	None	NA	NA

Remove Gap Only

Removes columns containing only gaps. This function is run by default, to not run this function specify --keep_gaponly.

Parameter	Description	Default Value	Min	Max
--keep_gaponly	Keep gap only columns in the alignment	False	NA	NA

Crop Divergent

Some alignments have a region which is clearly of higher quality than the surrounding alignment, with less diversity and fewer gaps. This can be the case when regions have been extracted, e.g. from a full genome, but the start and end positions of the region of interest are not well defined·

The crop divergent function redefines the start and end positions of an alignment by looking for crop_divergent_buffer_size consecutive columns which have a minimum proportion of identical residues >= crop_divergent_min_prop_ident and a minimum proportion of non-gap residues >= crop_divergent_min_prop_nongap, then taking the first or last such column as the alignment start or end.

Parameter	Description	Default Value	Min	Max
--crop_divergent	Crop either end of the alignment until > crop_divergent_min_prop_ident residues in a column are identical and > crop_divergent_min_prop_nongap residues are not gaps, over buffer_size consecutive columns	False	NA	NA
--crop_divergent_min_prop_ident	Minumum proportion of identical residues in a column to be retained by crop_divergent	divergent_min_prop_ident_def	divergent_min_prop_ident_min	divergent_min_prop_ident_max
--crop_divergent_min_prop_nongap	Minumum proportion of non gap residues in a column to be retained by crop_divergent	divergent_min_prop_nongap_def	divergent_min_prop_nongap_min	divergent_min_prop_nongap_max
--crop_divergent_buffer_size	Minumum number of consecutive columns which must meet the criteria for crop_divergent to be retained	divergent_buffer_size_def	divergent_buffer_size_min	divergent_buffer_size_max

Retain

These parameters allow the user to specify sequences which should not be removed from the alignment.

The sequences can be specified by providing one or more sequence names (--retain), a character string to match in the names (--retain_str) or a file containing a list of names (--retain_list).

The crop ends, remove divergent and remove short functions also have the option to specify sequence names to ignore with those specific functions only.

Parameter	Description	Default Value	Min	Max
--retain	Do not edit or remove sequences with this name when running any rowwise function (currently remove divergent, crop ends and remove short)	None	NA	NA
--retain_str	Do not edit or remove sequences with names containing this character string when running any rowwise function	None	NA	NA
--retain_list	Do not edit or remove sequences with names listed in this file when running any rowwise function	None	NA	NA

Visualisation functions

Each of these functions produces some kind of visualisation of an MSA.

Mini Alignments

These functions produce “mini alignments” - images showing a small representation of your whole alignment, so that gaps and poorly aligned regions are clearly visible. Mini alignment example

Output files:

• OUTFILE_STEM_input.png (or svg, tiff, jpg) - visualisation of the input alignment

• OUTFILE_STEM_output.png (or svg, tiff, jpg) - visualisation of the cleaned output alignment

• OUTFILE_STEM_markup.png (or svg, tiff, jpg) - visualisation of the input alignment with deleted rows and columns marked

Parameter	Description	Default
--plot_input	Plot a mini alignment - an image representing the input alignment	False
--plot_output	Plot a mini alignment - an image representing the output alignment	False
--plot_markup	Draws the input alignment but with the columns and rows which have been removed by each function marked up in corresponding colours	False
--plot_dpi	DPI for mini alignments	300
--plot_format	Image format for mini alignments - can be png, svg, tiff or jpg	png
--plot_width	Mini alignment width in inches	5
--plot_height	Mini alignment height in inches	3
--plot_keep_numbers	Label rows in mini alignments based on input alignment, rather than renumbering	False
--plot_force_numbers	Force all rows in mini alignments to be numbered rather than labelling e.g. every 10th row for larger plots Will cause labels to overlap in larger plots	False

Sequence logos

These functions draw sequence logos representing output (cleaned) alignment using the algorithm specified by [Schneider (1990)(]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC332411/).

Traditional “text” sequence logos can be produced as well as bar charts summarising the same information.

Text

Text logo example

Bar

Bar logo example

You can also specify a subsection of the alignment using the logo_start and logo_end arguments, positions should be relative to the input alignment. If no cleaning functions are specified, the logo will be based on your input alignment.

Output_files:

• OUTFILE_STEM_logo_bar.png (or svg, tiff, jpg) - the alignment represented as a bar chart

• OUTFILE_STEM_logo_text.png (or svg, tiff, jpg) - the alignment represented as a standard sequence logo using text

Parameter	Description	Default
--make_sequence_logo	Draw a sequence logo	False
--sequence_logo_type	Type of sequence logo - bar/text/both	bar
--sequence_logo_dpi	DPI for sequence logo	300
--sequence_logo_font	Font (see NB below) for bases / amino acids in a text based sequence logo	monospace
--sequence_logo_nt_per_row	Number of bases / amino acids to show per row in the sequence logo, where the logo is too large to show on a single line	50
--sequence_logo_filetype	Image file type to use for the sequence logo - can be png, svg, tiff or jpg	png
--logo_start	Start sequence logo	0
--logo_end	End of sequence logo	MSA length

NB: to see available fonts on your system, run CIAlign –list_fonts_only and view CIAlign_fonts.png

Statistics Plots

For each position in the alignment, these functions plot:

• Coverage (the number of non-gap residues)

• Information content

• Shannon entropy

Coverage

Information Content

Shannon Entropy

Output files:

• OUTFILE_STEM_input_coverage.png (or svg, tiff, jpg) - image showing the input alignment coverage

• OUTFILE_STEM_output_coverage.png (or svg, tiff, jpg) - image showing the output alignment coverage

• OUTFILE_STEM_input_information_content.png (or svg, tiff, jpg) - image showing the input alignment information content

• OUTFILE_STEM_output_information_content.png (or svg, tiff, jpg) - image showing the output alignment information content

• OUTFILE_STEM_input_shannon_entropy.png (or svg, tiff, jpg) - image showing the input alignment Shannon entropy

• OUTFILE_STEM_output_shannon_entropy.png (or svg, tiff, jpg) - image showing the output alignment Shannon entropy

Parameter	Description	Default
--plot_stats_input	Plot the statistics for the input MSA	False
--plot_stats_output	Plot the statistics for the output MSA	False
--plot_stats_dpi	DPI for coverage plot	300
--plot_stats_height	Height for coverage plot (inches)	3
--plot_stats_width	Width for coverage plot (inches)	5
--plot_stats_colour	Colour for coverage plot (hex code or name)	#007bf5
--plot_stats_filetype	File type for coverage plot (png, svg, tiff, jpg)	png

Palettes

This function sets the colour palette for the mini alignments. Currently available palettes are colour blind safe (CBS) and bright.

CBS

CBS palette

Bright Bright palette

Parameter	Description	Default Value
--palette	Colour palette. Currently implemented CBS (colourblind safe) and bright	CBS

Interpretation Functions

These functions provide additional analyses you may wish to perform on your alignment.

Consensus Sequences

This step generates a consensus sequence based on the cleaned alignment. If no cleaning functions are performed, the consensus will be based on the input alignment.

Consensus sequences can be majority - the most common character in each column is used, including gaps or majority_nongap - the most common non-gap character is used.

Where the two most frequent characters are equally common a random character is selected.

Once the consensus has been generated, gap positions are automatically removed, specifying ---consensus_keep_gaps prevents this.

Output files:

• OUTFILE_STEM_consensus.fasta - the consensus sequence only

• OUTFILE_STEM_with_consensus.fasta - the cleaned alignment plus the consensus

Parameter	Description	Default
--make_consensus	Make a consensus sequence based on the cleaned alignment	False
--consensus_type	Type of consensus sequence to make - can be majority, to use the most common character at each position in the consensus, even if this is a gap, or majority_nongap, to use the most common non-gap character at each position	majority
--consensus_keep_gaps	If there are gaps in the consensus (if majority_nongap is used as consensus_type), should these be included in the consensus (True) or should this position in the consensus be deleted (False)	False
--consensus_name	Name to use for the consensus sequence in the output fasta file	consensus

Position Frequency, Probability and Weight Matrices

These functions are used to create a position weight matrix, position frequency matrix or position probability matrix for your input or output (cleaned) alignment. These are numerical representations of the alignment which can be used as input for various other software, for example to find regions of another sequence resembling part of your alignment. PFMs, PPMs and PWMs are described well in the Wikipedia article here.

You can also specify a subsection of the alignment using the pwm_start and pwm_end arguments, positions should be relative to the input alignment.

Output_files:

• OUTFILE_STEM_pwm_(input/output).txt - position weight matrix representing the alignment (or part of the alignment)

• OUTFILE_STEM_ppm_(input/output).txt - position probability matrix representing the alignment (or part of the alignment)

• OUTFILE_STEM_pfm_(input/output).txt - position frequency matrix representing the alignment (or part of the alignment)

• OUTFILE_STEM_ppm_meme_(input/output).txt - position probability matrix representing the alignment (or part of the alignment) in the format used by the MEME software suite.

• OUTFILE_STEM_blamm_(input/output).png - position probability matrix representing the alignment (or part of the alignment) in the format used by the BLAMM software tool.

Parameter	Description	Default
--pwm_input	Generate a position frequency matrix, position probability matrix and position weight matrix based on the input alignment	False
--pwm_output	Generate a position frequency matrix, position probability matrix and position weight matrix based on the cleaned output alignment	False
--pwm_start	Start the PWM and other matrices from this column of the input alignment	None
--pwm_end	Start the PWM and other matrices from this column of the input alignment	None
--pwm_freqtype	Type of background frequency matrix to use when generating the PWM. Should be 'equal', 'calc', 'calc2' or 'user'. 'equal', assume all residues are equally common, 'calc', frequency is calculated using the PFM, 'calc2', frequency is calculated using the full alignment (same as calc if pwm_start and pwm_end are not specified).	equal
--pwm_alphatype	Alpha value to use as a pseudocount to avoid zero values in the PPM. Should be 'calc' or 'user'. If alphatype is 'calc', alpha is calculated as frequency(base) * (square root(n rows in alignment)), as described in Dave Tang's blog here, which recreates the method used in Wasserman & Sandelin 2004. If alpha type is 'user' the user provides the value of alpha as pwm_alphatype. To run without pseudocounts set pwm_alphatype as user and pwm_alphaval as 0	calc
--pwm_alphaval	User defined value of the alpha parameter to use as a pseudocount in the PPM.	1
--pwm_output_blamm	Output PPM formatted for BLAMM software	False
--pwm_output_meme	Output PPM formatted for MEME software	False

Similarity Matrices

Generates a matrix showing the proportion of identical bases / amino acids between each pair of sequences in the MSA.

Output file:

• OUTFILE_STEM_input_similarity.tsv - similarity matrix for the input file

• OUTFILE_STEM_output_similarity.tsv - similarity matrix for the output file

Parameter	Description	Default
--make_similarity_matrix_input	Make a similarity matrix for the input alignment	False
--make_similarity_matrix_output	Make a similarity matrix for the output alignment	False
--make_simmatrix_keepgaps	0 - exclude positions which are gaps in either or both sequences from similarity calculations, 1 - exclude positions which are gaps in both sequences, 2 - include all positions	0
--make_simmatrix_dp	Number of decimal places to display in the similarity matrix output file	4
--make_simmatrix_minoverlap	Minimum overlap between two sequences to have non-zero similarity in the similarity matrix	1

Editing Functions

Extracting part of the alignment

This function allows the user to specify a start and end position to isolate part of the alignment, using the –section_start and –section_end position. The section must be at least 5 residues in length. The section which has been isolated will then be used for all other processing with CIAlign.

If parsing functions are also specified, the positions output in the log files will be relative to the original input file, rather than the section.

Parameter	Description	Default
--get_section	Allows the user to specify a section of the alignment to be extracted and processed	False
--section_start	Start position in the original alignment for the section to be extracted	None
--section_end	End position in the original alignment for the section to be extracted	None

Replacing U or T

This function replaces the U nucleotides with T nucleotides or vice versa without otherwise changing the alignment.

Output files:

• OUTFILE_STEM_T_input.fasta - input alignment with T’s instead of U’s

• OUTFILE_STEM_T_output.fasta - output alignment with T’s instead of U’s

or

• OUTFILE_STEM_U_input.fasta - input alignment with U’s instead of T’s

• OUTFILE_STEM_U_output.fasta - output alignment with U’s instead of T’s

Parameter	Description	Default
--replace_input_tu	Generates a copy of the input alignment with T's instead of U's	False
--replace_output_tu	Generates a copy of the output alignment with T's instead of U's	False
--replace_input_ut	Generates a copy of the input alignment with U's instead of T's	False
--replace_output_ut	Generates a copy of the output alignment with U's instead of T's	False

Unaligning (removing gaps)

This function simply removes the gaps from the input or output alignment and creates and unaligned file of the sequences.

Output files:

• OUTFILE_STEM_unaligned_input.fasta - unaligned sequences of input alignment

• OUTFILE_STEM_unaligned_output.fasta - unaligned sequences of output alignment

Parameter	Description	Default
--unalign_input	Generates a copy of the input alignment with no gaps	False
--unalign_output	Generates a copy of the output alignment with no gaps	False